DO NOT REMOVE. Resource Guide. Electrical Systems. Training Center Copy ELTC9916A I N F I N I T I. Revised: January, 2012 START STOP ELTC9916A.

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1 NISSAN ELTC9916A Resource Guide LOCK Acc ON START STOP ENGINE Advanced Automotive Electrical Systems 14v 100% DO NOT REMOVE Training Center Copy ELTC9916A Revised: January, 2012 I N F I N I T I CREATED JANUARY, 2012

2 This book is designed for instructional use only for authorized Nissan North America, Inc. and Nissan dealer personnel. For additional information contact: Nissan North America, Inc. Technical Training P.O. Box Franklin, TN Nissan North America, Inc. All rights reserved. No part of this publication may be reproduced in any form without the prior written permission of the publisher. Printed in U.S.A. First Printing: DECEMBER, 2009 Second Printing: JANUARY, 2012 Training Department Nissan North America, Inc. Technical Training This manual uses post consumer recycled fibers Training Department Technical Training Nissan North America, Inc. reserves the right to alter specifications or methods at any time. ii

3 ADVANCED AUTOMOTIVE ELECTRICAL SYSTEMS RESOURCE GUIDE TABLE OF CONTENTS Text Introduction...1 Electrical Malfunctions Step Repair Procedure...2 Preliminary Diagnosis Tips...2 On-Car Troubleshooting Tips...2 Electrical/Electronic Fundamentals...3 Source, Load, and Ground...3 Electrical Terms...4 Voltage...4 Resistance...4 Amperage...4 Digital Multi Meter (DMM)...5 Digital Multi Meter (DMM) Safety Checklist...5 Voltmeter Use...6 Voltmeter Common Units of Measurements...6 Available Voltage...6 Voltage Drop...6 Testing Voltage Drop...7 Ohmmeter Use...8 Ammeter Use...9 Automotive Electronics...11 Relays...11 Types of Resistors...12 Semiconductors...13 Semiconductor Operation...13 Diodes...14 Construction of Semiconductor Diodes...14 Diode Operating Principles...15 Diode Applications...17 Testing Diodes...18 Transistors...19 Construction of a Transistor...19 Transistor Applications...20 Transistor Operation...20 Electronic Control Unit (ECU)...23 Operation...24 ECU Inputs...25 ECU Outputs...26 ECU Diagnosis...29 Body Control Module...30 iii

4 BCM Power Supplies and Grounds...30 ECU Input Components and Signals...32 BCM Outputs...35 BCM Controlled Systems...36 Combination Switches...38 MULTIPLEXING SYSTEMS...40 In-Vehicle Multiplexing System (IVMS)...41 Local Area Network (LAN) Systems...42 Controller Area Network (CAN) Systems...42 INTELLIGENT KEY SYSTEMS...49 Intelligent Key Unit Based Systems...49 Body Control Module (BCM) Based Intelligent Key Systems...51 Glossary...55 Notes Classroom Presentation Notes iv

5 ADVANCED AUTOMOTIVE ELECTRICAL SYSTEMS OBJECTIVES Upon completion of this course you will be able to: Read and interpret information from system schematics used in Nissan and Infiniti service manuals Read and interpret wiring diagram information from the three forms of wiring diagrams utilized in Nissan and Infiniti service manuals Predict voltage values at different points in a circuit using wiring diagrams or system schematics Diagnose system concerns using only the wiring diagram Locate diagnostic flow information in the service manual for electronically controlled systems Develop and use a logical approach to electronically controlled system diagnosis Configure CONSULT-III and the Measurement Interface (MI) to be used as a digital multimeter and an oscilloscope Diagnose concerns for systems controlled by the Body Control Module (BCM) Diagnose concerns for systems related to the Intelligent Power Distribution Module Engine Room (IPDM E/R) Diagnose concerns with the Intelligent Key Unit based Intelligent Key system Diagnose concerns with the BCM based Intelligent Key system Diagnose concerns in a Controller Area Network (CAN) systems using the CHECK SHEET method Diagnose concerns in a Controller Area Network (CAN) systems using the DIAGNOSIS SHEET method Diagnose concerns in a Controller Area Network (CAN) systems using CONSULT-III plus Identify special service requirements of the Body Control Module (BCM). Locate and perform self-diagnosis for the Vehicle Information Display Locate and use resources to pair a cell phone to a Nissan or Infiniti Hands Free Phone System v

6 COURSE PROCEDURES Class begins promptly at 9:00 a.m. Please be in your seat and ready to begin at 9:00 a.m. Please silence your cell phones. Class ends when all the modules on the sign-off page of your guidebook are initialed by the instructor. Nissan designs training so that most technicians should be able to complete all activities in the time allotted for the course. If you are unable to complete the requirements of the course in the time provided, you instructor will discuss options with you to receive course credit. You are responsible for learning the techniques and procedures featured in this course. It is important you take as much time as you need to learn the skills presented in the course material. If you cannot complete the requirements of the course in the time provided your instructor will work with you and your dealership and help you complete the course. Text and PowerPoint Notes: The Text Section and PowerPoint notes are provided for reference during the course in the Resource Book provided by the instructor. The Resource Book must be returned at the end of the class. Refer to the PowerPoint notes to follow the classroom presentation. The classroom discussion highlights information you will practice during completion of the modules. Make notes and ask questions during the discussion and you will learn information that will help you complete the worksheet objectives. Blank pages are provided in the back of the Student Guide for taking notes during the class. The Text Section is a available for download in Virtual Academy. Course Map: The course map indicates the order in which the modules should be completed. In the case of some training courses, certain modules must be completed before you begin other modules. Modules: 1. Begin the module by reading the Objective, Relevance, Resources, and Skill Check on the first page. This information will present the basis for the skills included in the module. 2. Read each step carefully to determine the appropriate actions or procedures the modules is designed to impart. 3. Pay attention to the Notes, Cautions, and Service Tips included in the module. In many instances they will help you derive the answer to questions included in the module and will help you develop the skill sets intended by the design. 4. You will probably be working with one or more technicians during this course. Follow these basic guidelines to work effectively as a team: Take responsibility to understand and perform each step yourself. vi

7 When using diagnostic tools (CONSULT, multi-meters, etc.) be sure to check the onscreen results yourself and hand the tool to the other members of your group so they can confirm the results as well. If you are expected to test or remove and inspect a component, perform these procedures yourself and give the same opportunity to other members of your team. Be patient. Everyone works at different speeds.you are responsible to be able to perform each module objective - and you are responsible to insure others working with you can complete the skill check. Complete all questions on the worksheet. In some cases, the worksheet may give you the opportunity to skip some steps, for example - you may not need to follow the instructions for booting CONSULT if you are already confident using the tool. If your co-workers wish to complete these instructions, be patient as they perform these steps. Treat the training center vehicles as if they were a customer s car. However if you damage a vehicle in the course of completing a module, notify the instructor immediately. Some components such as trim pieces or wire connectors may be damaged during testing. We expect these occasional problems and need to know about them as soon as they occur. Return the vehicle to the condition it needs to be in for the next group of technicians to complete the workstation. For example; reset the bugs if applicable, return tools to the workbench or tool box and straighten up the work area. Contact the instructor when you have completed the module and are confident you can perform the Skill Check stated on the first page. Expect the instructor to review your worksheet and confirm that you have completed the objective. Tell the instructor if you feel you need more practice.if possible, the instructor will provide you with additional information or give you the opportunity to work on the vehicle later that day. Resources: Resources may include ASIST, CONSULT, service manuals, digital multi-meters, hand tools, special service tools, and vehicle parts. If the ASIST terminal is not working properly or has not been updated, please notify your instructor. Monitor the battery power for CONSULT and connect it to the charger as needed. For some courses we expect you to be comfortable using CONSULT for testing the CAN system and accessing Self Diagnosis, Data Monitor, Active Test and Work Support. Contact your instructor if you are not familiar using these applications.contact the instructor if you have any questions about using the listed resources or there is a problem with any of the resources you will need to complete the module. vii

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10 Introduction ADVANCED AUTOMOTIVE ELECTRICAL SYSTEMS In this course we will explore a number of electrically and electronically controlled systems along with communication systems such as CAN used on Nissan and Infiniti Vehicles. Systems we will explore are: Power Window Systems Intelligent Key Systems Head lamp Systems Controller Area Network Systems (CAN) Bluetooth Hands Free Phone Systems Vehicle Information Display Systems Intelligent Power Distribution Module and Related Systems Vehicle Security Systems Body Control Module and Related Systems Automatic Back Door Systems Most of these systems are electronically controlled and have many common features. The CAN systems, in addition to being electronically controlled, use multiplexing technology to share information between many different control units or processors. Before we proceed with discussions on these individual systems, we will review a few electrical basics along with the basics of electronically controlled systems Electrical Malfunctions Most malfunctions that occur in electrical circuits are due to circuit resistance being either abnormally high or abnormally low. This will usually be caused by wiring or connection problems. For example: Increased resistance can be caused by loose connections, corroded wire connectors or dirty switch contacts. These conditions create unwanted resistance that reduces the normal current flow needed to operate the load. Symptoms associated with increased (unwanted) resistance would be a bulb the burns dim or a motor that turns slowly, to name a few. An open circuit is the extreme side of increased resistance and can be caused by broken wires, backed-out terminals, disconnected connectors or failed loads. An inoperative load is the most commonly associated symptom when an open occurs. Advanced Automotive Electrical Systems 1

11 Decreased circuit resistance increases current flow in a circuit. This can be caused by a short to ground on the source side of the circuit or a shorted load. Symptoms associated with decreased circuit resistance would be an inoperative load due to a blown fuse or circuit breaker. Also, in some cases, higher than normal current flow can overheat and burn wires and/or connectors. 4 Step Repair Procedure Diagnosing electrical malfunctions, like any other vehicle system, involves investigating the cause of the problem and reaching a conclusion based on your investigation. Accurate diagnosis requires understanding how the specific system functions, then evaluating whether it functions as designed. Basic diagnosis involves the following steps: 1. Verify - Apply knowledge and use reference materials to find possible causes 2. Isolate - Inspect and/or test for the system fault in a logical order 3. Repair or replace component at fault 4. Recheck Confirm fault / complaint is corrected as well as no new concerns have developed Preliminary Diagnosis Tips Step 1: For unfamiliar circuits, start with the wiring schematic or wiring diagram. This provides an overview of the circuit. The schematic diagram shows circuit components and how they are connected. Always locate the circuit load first, then trace the wires back to the battery (source side) and then to ground (ground side), if necessary. Check fuses and fuse links protecting the circuit in question. Step 2: Use the wiring diagram for a complete picture of the circuit. The wiring diagram is the best source to logically trace the circuit. It includes information such as wire colors, connector numbers and relay box layout. Use your knowledge of source, load and ground along with the wiring diagram to help isolate the circuit for testing. Step 3: The Harness Layout section of the service manual describes specific harness and connector locations on the vehicle. The harness layout diagram will help you find the exact locations on the vehicle to perform your diagnosis. Step 4: Finally, locate the actual components and the most accessible test points by using the Location of Electrical Units section of the service manual. On-Car Troubleshooting Tips Always check the source voltage (at the battery) before testing circuit voltage. Visually inspect the battery connections for looseness or corrosion. Clean and tighten battery cables as necessary. 2 Advanced Automotive Electrical Systems

12 Check available voltage at the load and compare it to the source voltage. If it is not the same or nearly the same, there is an abnormal voltage drop between the battery and the load. Look for poor connections, frayed wires, etc. Check for blown fuses and check for poor contact /missing fuses. Check tightness and the condition of ground connections. Simulate the conditions of the problem. NOTE: The GI Section of the Service Manual contains helpful information on different test methods for locating electrical malfunctions. Also, remember to check ASIST for relevant service bulletins or tech tips. One thing to remember, no matter how complex the system you are working on, a sound understanding and application of electrical basics will always make the process easier. With that in mind, let's review some of these electrical fundamentals. Electrical/Electronic Fundamentals Source, Load, and Ground Every electrical circuit has 3 essential elements (sections). They are: SOURCE (voltage) LOAD GROUND Without these, the circuit will not work. Let's go a little deeper and define these. SOURCE - The source of voltage is the battery or alternator. The voltage source provides the energy to push current through the circuit to make it operate. LOAD - A load is the device that produces heat, light, sound or motion when the circuit is operating. Light bulbs, motors and heating elements such as cigarette lighters and rear window defoggers are typical electrical loads. GROUND - A ground completes the circuit from the load back to the negative battery post. As important as the ground is, it is the part of the circuit that is most often overlooked. Source side of circuit Ground side of circuit Battery Wire Load Wire Advanced Automotive Electrical Systems 3

13 As you can see from the graphic and following the arrows (flow), every electrical circuit starts at battery positive (source) and goes to the load then follows the ground back to the battery negative (this is often referred to as 'conventional' current flow). This makes a complete circuit. If any of these essential elements is missing or not working properly, there is diminished or no current flow and the circuit will not operate properly. Electrical Terms Voltage (Symbol V) Voltage is the electrical pressure that pushes current through a circuit. Voltage is measured using a voltmeter and is stated in volts (V) or milli-volts (mv) 1 mv = V (Example: 25 milli-volts = volts). The most common voltage on a vehicle is battery voltage (12 volts). Battery voltage will increase from the charging system with the engine running (14.0 to 14.7 V The second most common voltage on vehicle today is 5 volts, used on vehicle systems sensor circuits. Being able to test circuits for specific voltages is critical to the proper testing and diagnosing of electronic circuits. Resistance (Symbol Ω ) Resistance opposes current flow in the circuit. Resistance is measured using an ohmmeter and is stated in Ohms ( Ω ), K Ohms (K Ω ) or Mega Ohms (M Ω ) 1,000 Ω = 1 K Ω = M Ω (Example: 25 ohms = K ohms = 0.000,025 M Ω ) The amount of resistance in a circuit determines the amount of current flow through the circuit. According to Ohms Law (E = I x R) if the resistance in a circuit decreases, the current flow increases or if the resistance in a circuit increases the current flow in the circuit decreases. The resistance in a circuit also determines the amount of voltage drop across the resistance. The greater the resistance the greater the voltage drop will be across the resistance. Amperage (Symbol A) Amperage is the measurement of current flow in a circuit. Current flow is measured using an ammeter and is stated in amperes or Amps (A) and milli-amps (ma). 1mA = A (Example: 25 milli-amps or Amps) Current flow on today s vehicles can range from a high of around 200 Amps in the starter circuit to a low of around 40 Micro amps (40 millionths of an amp) in a computer. Any change in resistance in a circuit will affect the current flow in a circuit. 4 Advanced Automotive Electrical Systems

14 Something as simple as connecting the wrong meter or test light to a circuit could increase the current flow in the circuit and possibly damage the circuit or components in the circuit. Digital Multi Meter (DMM) The most common type of meter used for testing automotive electronic circuits is the Digital Multi Meter (DMM). The DMM actually combines three meters in one: Ohmmeter- measures resistance Voltmeter Measures voltage Ammeter measures amperage NOTE: It is very important to use a DMM with at least 10 MÙ(10 million Ohms) internal resistance when performing tests on computer circuits. Using a meter with less than 10 MÙ internal resistance could cause damage to the circuit or components. Digital Multi Meter (DMM) Safety Checklist: Follow all equipment safety precautions. Be certain the meter is in good operating condition. Use a meter that meets accepted safety standards. Use a meter with fused current inputs. Be sure to check meter fuses before making current measurements. Only use meters with recessed input jacks. Inspect test leads for physical damage before making a measurement. Use the meter to check continuity of the tests leads. Only use test leads that have shrouded connectors and finger guards. Select the proper function and range for the measurement you intend to make. Always disconnect the red (+) test lead first. Use a meter, which has overload protection on the Ohms function. When measuring current without a current amp clamp, turn the circuit power OFF before connecting into the circuit. Use extreme caution in high current and high voltage testing situations. Use the appropriate equipment, such as high voltage probes and high current clamps, for your personal safety. Advanced Automotive Electrical Systems 5

15 Voltmeter Use A voltmeter is the most commonly used and most versatile of all automotive electrical testers. A voltmeter has two functions: Measuring available circuit voltage Measuring voltage drop Voltmeter Common Units of Measurements Volts AC/DC (example = 2.9 V) milli-volts (example = 2900 mv) Available Voltage Checking for available voltage measures the voltage available up to the location on the circuit to which the meter is connected. In a normal circuit, there should be source (battery) voltage available up to the load. Since the battery provides a constant 12 volts or more if the vehicle is running, any excessive resistance in the circuit will reduce the available voltage to operate the load. Reduced available voltage results in dim light bulbs, slower spinning motors and relay coil circuits that don't have enough energy to close the contacts. To measure available voltage: Step 1: Select voltage (DC (V) or AC (V~) setting on your meter. Note: If circuit voltage is unknown, use the scale closest to, but higher than 12 volts. Step 2: Connect the voltmeter probes between the test point in the circuit and a known good ground to obtain a voltage reading. Observe the polarity of the meter when making these connections. In other words, connect the red lead (+) to the point closest to the battery and the black lead (-) to the connection toward ground. Step 3: Operate the circuit being checked and read the voltage on the meter display. Service Tip: You can also use a test light to test high current, NONELECTRONIC circuits. A test light can test bulb circuits, relay circuits and fuses for available voltage. However, a test light CANNOT measure the amount of available voltage, a decided disadvantage. Voltage Drop Perhaps the biggest electrical problem faced by technicians is that of unwanted resistance in a circuit. All loads in a circuit have resistance and use voltage. Voltage drop is the amount of voltage consumed by a load in a circuit during operation and is measured using a Volt meter. Unwanted resistance creates a voltage drop in other parts of a circuit, such as at connection 6 Advanced Automotive Electrical Systems

16 points, and this can affect circuit operation. Performing a voltage drop test on a circuit is an excellent method of diagnosis that should be used to test the circuit integrity. The amount of voltage drop in a circuit is determined by the amount of resistance in an operating circuit. The greater the resistance in any part of a circuit, the greater the voltages drop. A general specification for allowable voltage drop in automotive wiring circuits is 0.1 volt per connection. When measuring resistance with an ohmmeter, contact by a single strand of wire would provide a reading of 0 Ω. This would indicate a good circuit. But when the circuit operates, this single strand of wire is unable to carry the current. The single wire will have created a high resistance to the current flow. This will be picked up as a voltage drop. Testing Voltage Drop Step 1: Connect the voltmeter across the connection or portion of the circuit to be tested. The positive lead (red) of the voltmeter should be on the side to the source (+) The negative lead (black) on the side to the ground (-). Step 2: Operate the circuit. Step 3: The voltmeter will indicate how many volts are used by that part of the circuit. Source Voltage 12.0V 0.1V OK 3.9 V Excessive Voltage Drop Dim Bulb 12 volts Resistance 0.1V OK 7.9 V Low Advanced Automotive Electrical Systems 7

17 Because a circuit must have source, load and ground to operate, check the ground side of a load for voltage drop as well. Look for bad ground connections at the vehicle frame, corrosion at the negative post of the battery and loose ground straps or connections at components such as the starter motor and alternator. Just because your eyes tell you the connection is good it does not mean it is. Rule of Thumb for maximum Voltage Drops at Connections: * Wire Connections: less than 0.1 Volts * Ground Connections: 0.1 Volts * Switch Contacts: 0.3 Volts * Starter Solenoids: 0.5 Volts * Sensor Grounds: less than 0.05 volts Ohmmeter Use An ohmmeter has two important functions: Measuring circuit or component resistance. Checking continuity in a circuit or a component. Common units of measurements: Ohms ( Ω ) K Ohms(1,000 ohms = K Ω ) Mega Ohms (1,000,000 ohms = M Ω ) All circuits must have resistance to operate correctly. As voltages in most automotive circuits are fairly constant the current flow through a circuit is determined by the resistance in the circuit. High Resistance in a circuit As the resistance in a circuit increases the current flow decreases. A common cause of high resistance in a circuit is poor connections. Terminal corrosion Loose terminals Low resistance in a circuit A short in a component could cause low resistance in a circuit. A shorted relay coil would cause the resistance to decrease and the current flow to increase. 8 Advanced Automotive Electrical Systems

18 NOTE: Never use an ohmmeter on a circuit while it is operating. This may damage the meter. The component or circuit being measured should be isolated from the rest of the circuit How an Ohmmeter Works An ohmmeter sends a small voltage out one lead and measures how much of the voltage comes back to it. Most meters send out a 0.5-volt signal. This is why the circuit must be isolated from any voltage source. This includes but is not limited to the battery, any module or computer in the circuit. If you leave a module plugged into a circuit while performing a resistance test on the circuit, the internal components of the module could dissipate voltage and falsify your readings. To Use an Ohmmeter: Step 1: Select the Ω position on your meter Step 2: Check meter calibration by touching the two test leads together. Typical test lead resistance is between 0.2 Ω and 0.5 Ω. You will need to subtract this reading from your final reading or use the Zero button on the DVOM (refer to DVOM operators manual). Step 3: Be sure the circuit being checked is switched OFF. Never use an ohmmeter on a circuit while it is operating. The ohmmeter has an internal battery. Additional voltage through the meter may damage it if the meter does not have overload protection. Step 4: Connect the meter leads to the ends of the circuit or component to test and read the resistance. NOTE: If OL appears on your meter the range may be set too low. Select a higher scale, K Ω or M Ω. Ammeter Use An ammeter measures current flow in a circuit. If specifications are available, amperage (current) readings can be helpful during diagnosis. Common units of measurements Amps milli-amps Advanced Automotive Electrical Systems 9

19 To use an ammeter: Step 1: Connect the ammeter in series in the circuit. This means that all the current flowing in the circuit will flow through the meter. Some hand-held meters can only measure up to 2 amps. Some meters have the capability to measure up to 10 amps. CAUTION: THE AMMETER IS NOW PART OF THE CIRCUIT AND EXCESSIVE AMPER- AGE, WHICH COULD OCCUR IN A SHORT CIRCUIT, CAN DAMAGE THE AMMETER OR AMMETER FUSE. ALWAYS CHECK FUSES ACCORDING TO THE METER INSTRUCTIONS. Step 2: Connect the positive lead of the ammeter toward the battery positive (+) terminal and the negative ammeter lead to the ground or negative ( ) side of the circuit. Step 3: Switch the circuit ON A 12 volts 10 Advanced Automotive Electrical Systems

20 An amperage reading above specifications indicates low circuit resistance. - Short circuit - Slow turning motor An amperage reading lower than specification indicates high circuit resistance - Weak battery - Defective charging system - Excessive circuit resistance (corrosion, poor connections) Inductive Ammeter Clamps (pickups) Many ammeters have an inductive pickup instead of separate leads. Inductive ammeters are both accurate and easy to use without becoming part of the circuit. Inductive clamps can be used if the amount of current being measured is larger than the maximum current flow rating of the meter. The major advantage of using an inductive amp clamp is that the circuit does not need to be broken to measure the current flow. Inductive ammeter clamps are connected to the voltmeter inputs of a DVOM. The DVOM is usually set on the lowest voltmeter scale (mv). An inductive ammeter clamp measures the strength of the magnetic field created around a wire when a current is flowing through the wire. The inductive ammeter clamp then converts the measurement to a voltage reading on the DVOM. The reading on the DVOM is then converted from a table or calculation to an AMP reading. Automotive Electronics Today, control modules (computers) are being used in most Nissan automotive systems. Some examples of systems that use control modules that will be studied in this course will be the Body Control Module, Intelligent Power Distribution Module, Automatic Back Door Control Unit and the Audio Visual (AV) Control Unit. As you learned in the basic electrical course a computer looks at a number of inputs then compares the inputs to a program in the computer to determine the correct output. To accomplish this, the computer uses a number of components inside the control units such as integrated circuits, memory chips, diodes, relays, transistors and resistors. It is unlikely that you as a technician will have to replace specific electronic components such as transistors or diodes inside of a computer module but it is important to understand the operation of these components to aid in a proper diagnostic sequence. Let s name and explain the function of some of the components we could find inside of or integral to a control module. Relays Relays are not part of a control module but are used by modules to connect two parts of a cir- Advanced Automotive Electrical Systems 11

21 cuit. Relays use low amperage circuits to control a higher amperage circuit. Relays have two or more separate circuits: Coil control circuit (low current) Contact circuit (high current) The control circuit contains a coil of fine wire which, when energized, develops a magnetic field. The contact circuit contains a spring-loaded switch arm connecting the relay contacts when the control circuit is energized. The magnetic field pulls the metal armature which in turn closes the contacts. An important aspect to remember is just because a relay makes a clicking sound when engaged it does not mean the contacts are letting the current through. When diagnosing a relay both parts of the relay must be checked, this means the coil (low current flow) and contact (high current flow) sides are checked individually. Like switches, relays can have normally open (NO) or normally closed (NC) contacts. In wiring diagrams, hollow circles represent normally open relay contacts. Darkened circles represent normally closed relay contacts. There are four types of relays used on vehicles: 1. 1M (One-Make Relay) 2. 2M (Two-Make Relay) 3. 1T (One-Transfer Relay) 4. 1M-1B (One-Make, One-Break Relay) Types of Resistors Before we start we need to remember that all loads are resistors. A simple lamp is a resistor, a 12 Advanced Automotive Electrical Systems

22 horn is a resistor and a fan motor is a resistor. All components that turn electricity into sound, motion, heat or light are resistors Today vehicles use a variety of fixed and variable resistors on the vehicles. Potentiometers, Thermistors and photo resistors are examples of resistors that are used for inputs to the different control units. (BCM, ECM, Etc.) Semiconductors Semiconductors have revolutionized the automotive electronics industry. The use of semiconductors has enabled designers to create control units that are very compact and use very small amounts of current flow. Semiconductor Operation If you recall back to your electrical theory the atomic makeup of a material determines its electrical characteristics. A material that has less than 4 electrons in its outer valence ring is known as a good conductor, a material that has 4 electrons in its outer valence ring is known as a semiconductor and a material that has more than 4 electrons in its outer valence ring is known as an insulator. Some examples of materials that have these characteristics include: Copper Good conductor 1 electron in its outer valence ring Silicon Neither a good conductor nor a good insulator 4 electrons in its outer valence ring Insulator Insulator More than 4 electrons in its outer valence ring As mentioned above a semiconductor material is neither a good conductor nor a good insulator. The most common type of semiconductor material used is Silicon. For use in computer circuits the silicon s electrical characteristics must be changed. To change the electrical characteristics of the silicon designers use a method called Doping. Doping is a method of adding impurities to the semiconductor material. The type of impurity added to the silicon will determine the materials electrical characteristic. Adding the impurities arsenic, phosphorous or antimony will create a semiconductor with an excess of electrons. This will be known as an N type semiconductor. Adding the impurities boron, indium or gallium will create a semiconductor with an absence of electrons. This will be known as P type semiconductor. By changing the electrical characteristics of the silicon material the material will now be a better conductor of electrons or a better acceptor of electrons. Advanced Automotive Electrical Systems 13

23 N type Silicon semiconductor -Doping materials are arsenic, antimony or phosphorous -Creates an outer valence ring with an excess of electrons -Creates a semiconductor material with an excess of electrons -Good conductor of electricity P type Silicon semiconductor -Doping materials are boron, indium or gallium -Creates an outer valence ring with an absence of electrons (known as holes in the valence ring) -Creates a semiconductor material with an absence of electrons -Creates a material that can accept electrons By combining the above types of semiconductor materials designers can manufacture compact, low cost components that use a very small amount of current flow (such as diodes and transistors). Diodes The purpose of a diode is to allow current flow in one direction only. Diodes can be compared to one-way valves in hydraulic circuits. Clamping, light emitting and Zener diodes are various types of diodes used in automotive applications. Diode Symbol (PN Diode) Anode (+) Cathode (-) Direction of Current Flow Construction of Semiconductor Diodes To construct a semiconductor Diode a piece of P type material is joined to a piece of N type material. The difference in electrical characteristics between the materials causes some electrons to move from the N type material to the P type material. As the movement of electrons becomes balanced a junction is formed between the 2 materials. The junction acts as resistance to any further movement of electrons. To make the diode operate the junction size needs to be changed. This can be accomplished by connecting a battery to the diode. Adding a battery in 14 Advanced Automotive Electrical Systems

24 the same polarity as that of the diode causes the junction to be made smaller and allows current to flow. Adding a battery to the diode in the reverse polarity causes the junction to become larger. A larger junction will not allow current to flow. P type material N type material Diode Operating Principles Junction or Depletion area Forward Bias - a diode will allow current flow if the voltage applied to the diode is the same polarity as the diode Reverse Bias - a diode will not allow current flow if the voltage applied to the diode is opposite to the diode polarity. Diode Operation (Forward Bias-Turned on) NOTE: To explain the operation of a diode the electron theory of current flow will be used. The electron theory states that current flows from negative to positive To turn the diode on the junction must be made smaller. This is accomplished by connecting a battery to the diode with the same polarity as the diode. When the battery is connected to the diode the electrons in the negative post of the battery repel the excess electrons in the N type material towards the junction of the diode. (Remember like charges repel and unlike charges attract) At the same time the positive post of the battery repels the holes in the P type material towards the junction. Movement of the electrons and holes toward the junction makes the junction smaller. Because the junction is now smaller and has less resistance to the movement of electrons, the electrons in the negative post of the battery are now allowed to pass through the diode to the Positive post of the battery. The diode has been turned on (forward biased). In the example below forward biasing allows current flow through the diode and the lamp turns on. The voltage drop through the diode will be 0.5 volts to 0.7 volts. Advanced Automotive Electrical Systems 15

25 Forward biasing turns ON the load 12 volts Diode Operation (Reverse Bias-Turned off) To turn the diode off the junction must be made larger (wider). To accomplish this, the battery must be connected to the diode in the reverse polarity of the diode. When the battery is connected in the reverse polarity the positive post of the battery attracts the electrons in the N material. (Remember like charges repel and unlike charges attract) At the same time the Negative post of the battery attracts the holes in the P type material. The movement of the holes and electrons away from the junction causes the junction to become larger (wider). This causes a resistance to electron flow and as a result current flow stops. The diode has been turned off (reverse biased). Reverse biasing turns OFF the load 12 volts 16 Advanced Automotive Electrical Systems

26 Diode Applications Rectification: The most common automotive example of rectification occurs in the alternator. A rectifier bridge in an alternator is constructed of 3 negative diodes and three positive diodes. The rectifier bridge is connected to the stator windings in the alternator. The combination of diodes converts the alternating current from the stator into a direct current flow, which can be used to charge the battery and run the vehicles electrical systems. Can also be used to drop the voltage in a circuit. A typical example of this application would be if a specific voltage drop was required through a circuit. By placing more than one diode in the circuit in series the voltage through the circuit will be dropped the required amount. Protection devices (clamping diodes) A typical example of this application would be in a relay control circuit. By placing a diode across the coil in the computer controlled load, such as an ignition coil or injector, the driver circuit in the computer is protected from a voltage spike. One of the most common uses of a diode is in the ECU relay control circuit. The diode is used across a relay coil to absorb the voltage spike when the circuit is turned off. In the example the Load is controlled by the control unit. Switch closed When the switch in the control unit is closed, current flows through the circuit and the load is turned on. The undesirable affect of current flowing through a coil of wire, is that a magnetic field is built up around the coil of wire. Switch opens When the switch opens the current flow stops and the load turns off. However the magnetic field that was created around the coil collapses. The collapse of the magnetic field causes a Advanced Automotive Electrical Systems 17

27 voltage to be induced (in the reverse direction of the battery) into the circuit. To keep the induced voltage from damaging the driver circuit or switch in the control unit, a diode is placed across the coil of wire. The diode redirects the induced voltage and the voltage is dissipated across the coil of wire. Testing Diodes Testing a diode requires the use of a DVOM set in the diode test position. Step #1: Set the DVOM in the Diode test position Step #2: Connect the leads of the DVOM to the diode Step #3: Record the reading from the DVOM (may show OL or 0.7) Step #4: Reverse the leads on the diode Step #5: Record the reading on the DVOM (may show OL or 0.7) Test Results: The DVOM should show 0.7 volts with the leads connected one way and then should show OL with the leads reversed. This occurs because the Ohmmeter is supplying a small voltage to the diode. With the DMM connected in one direction you are forward biasing (turning on) the diode and with the leads reversed you are reverse biasing (turning off) the diode. Other Types of Diode Applications LED (Light emitting diode) Light emitting diodes have many uses in automotive applications. Typical uses of LEDs are in instrument clusters or audio systems. An LED is different than a regular diode in that the LED emits a light when forward biased. LED Symbol LED Operation As voltage is applied to an LED, in a completed circuit, current starts flowing through the LED. The movement of electrons from one band to another band releases Photons (energy). Photons are the basic unit of light. While photons are produced in regular diodes, the energy level produced is very low. As a result the amount of light produced cannot be seen by the naked eye. 18 Advanced Automotive Electrical Systems

28 The further the electron has to move from one band to another determines how bright the light is and what the color will be. LEDs are specially constructed to release a large number of photons outward. Additionally, they are housed in a plastic bulb that concentrates the light in a particular direction. LEDs can be used singularly or they can be grouped in what is known as seven segment diodes. Seven segment diodes will be used to show number displays. NOTE: -When inserting an LED into a circuit it is very important that a resistor is placed in the circuit to control the amount of current flow through the striate. -The longest lead on the LED is the Anode and should be connected to the most positive point of the circuit. -The voltage drop across an LED is 1.5 volts 2.2 volts Zener Diodes Zener diodes are used in a circuit where a fixed voltage output needs to be controlled. A common use for a Zener diode would be in an electronic voltage regulator. Zener Diode Symbol Zener Diode Operation Zener diodes are designed to 'breakdown' in reverse to maintain a fixed voltage across their terminals. The diodes are designed to stop the current flow up to a specific voltage setting. At a specific voltage setting the diode will turn on and allow current flow, bypassing a part of the circuit. Transistors The purpose of a transistor is to control a circuit that uses a large amount of current flow with a circuit that uses a small amount of current flow. A transistor is an electronic relay. Two common uses of transistors in automotive applications are as switches and amplifiers. Construction of a Transistor The construction of a transistor is similar to the construction of a diode except that two junctions are formed. The transistor components can be identified as the emitter, collector and the base. Advanced Automotive Electrical Systems 19

29 Transistor Symbols Transistor Applications Output Drivers Transistors are used in control units to control the operation of output devices Ignition Control Transistors are used in ignition control modules to control the switching of the primary ignition circuit. Transistor Operation Transistor operation can be broken down into two circuits. They are the Base to Emitter circuit and the Emitter to Collector circuit or the Collector to Emitter circuit. The Base Emitter circuit is the circuit that is used to turn the transistor on and off. Applying a small amount of voltage to the Base causes a small amount of current to flow from the Base to the Emitter. 20 Advanced Automotive Electrical Systems

30 This small amount of current flow allows a larger current flow from the Emitter to the Collector. The increase in current flow is transistor gain. Transistor Controlled Circuit Advanced Automotive Electrical Systems 21

31 Darlington Pair Transistors In some cases the amount of current flow in an output circuit may exceed the allowable current flow through a single transistor. In this case a Darlington pair transistor may be used. Sometimes called a piggyback transistor the Darlington pair transistor uses 1 of the transistors to turn on the other transistor. Using 2 transistors can increase the amount of current flow needed to operate the output device. Operation Small voltage signal is sent base of TR1 This turns on the B-Emitter circuit of TR1 With the B-E circuit turned on current is allowed to flow from the Collector to the emitter of TR1 The collector emitter circuit of TR1 Turns on the Emitter - base circuit of TR2 With the E-B circuit turned on in TR2 current flows through the Emitter- Collector circuit of TR2 which operates the load NOTE: The purpose of using a Darlington pair is to increase the amount of current through the circuit. If each transistor had a gain of 10 then we could see from the example below that the current flow of 10 milli-amps in the B-E circuit of TR1 has increased to 1000 milli amps current flow in the TR2 Emitter-Collector circuit. 22 Advanced Automotive Electrical Systems

32 Example: TR1 Base emitter current flow 10 milli-amps TR1 Collector emitter current flow 10X10= 100 milli-amps TR2 Emitter Base current flow 100 milli-amps TR2 Emitter Collector current flow 10X 100 = 1000 milli-amps Integrated Circuits Most computer circuits are not constructed of wires or terminals, as we know them. An integrated computer circuit is built on a thin wafer of silicon. Usually manufacturers will reproduce identical circuits on a larger piece of silicon and then cut the IC apart. The IC may then be combined with other integrated circuits on a larger wafer strip to form complete electronic circuits. On the thin silicon wafer will be mounted many conductors, diodes, transistors and resistors that make up the electronic circuit. The IC circuits are then installed in a case such as the BCM or the ECM. As a technician you will usually not have to replace individual circuit boards, but it necessary to know certain safety measures that should be observed when working on control units that contain IC boards. 1. Always ground yourself when working on or around control units. By grounding yourself you are protecting the control unit from static electricity. 2. Do not touch the control unit terminals. Grease and acids from your fingers can cause corrosion on the terminals. 3. Do not touch any meter terminals to the control unit terminals. 4. Do not apply any voltage to any terminals on the control units. 5. Always make sure the control unit is properly grounded before turning on the ignition. Electronic Control Unit (ECU) As you may recall from previous studies, electrical loads and the flow of current are controlled in different ways, depending on the complexity of the circuit. In some circuits, for example, a simple switch controls their operation. At other times, relays or electronic controllers are used in addition to a switch. Electronic controllers are commonly used on Nissan and Infiniti electrical systems and the circuits covered in this course are no exception. The primary difference between simple electrical circuits and electronic circuits is that in simple electrical circuits, the circuits have moving parts. Examples are mechanical switches and relays. Electrical switches are normally open or normally closed. Always refer to the service manual wiring diagram or system diagnostic procedure to determine the correct switch position and voltage when testing circuits. Electronic circuits, on the other hand, have no moving parts where the switching is a accomplished via a transistor within the ECU. Another example of an electronic part is a diode that is used to control the path current flows. Advanced Automotive Electrical Systems 23

33 The ECU in a circuit compares the input signals it receives with data stored in its memory. This type of analysis by the ECU results in an output from the ECU. To process input signals and to produce outputs, ECUs have two operating memories: Read Only Memory (ROM) and Random Access Memory (RAM). Read Only Memory (ROM) is permanently programmed with the operating data necessary to control output. Random Access Memory (RAM) can create and store new data in addition to reading previously stored information. As the following graphic shows, electronic controllers must have input from sensors to determine when to switch a circuit on or off. Operation Electronic circuits are unique because an ECU uses internal logic, circuitry and memory to control circuit operation. Relay and switch circuits do not have these capabilities. Circuits controlled by electronic control units require the following: Input - Sensors provide electrical signals to the ECU, which provide information about vehicle (system) conditions or operator requests. Logic - The ECU processes all electrical inputs and determines when, what and how long an output signal is sent to a LOAD. Output - An electrical signal provided by the ECU that controls the operation of a LOAD. In some cases, an output could be a signal sent from one ECU to another ECU as a data signal. 24 Advanced Automotive Electrical Systems

34 ECU Inputs ECUs receive input signals from numerous types of devices: potentiometers, piezoelectric devices, thermistors, variable reluctance sensors, hall-effect type sensors and switches to name a few. These input signals report information to the ECU. The ECU uses this information to determine how to control output devices (loads). ECU inputs can be divided into two types: ANALOG - A variable signal that is proportional to a measured quantity; such as temperature, speed or position. Examples of devices that generate Analog signals are: Throttle Position Sensor (potentiometer) Ambient Temperature Sensor (thermistor) Vehicle Speed Sensor (variable reluctance sensor) Analog input signal voltage varies and may change from high and low in an irregular pattern. Analog Signals DIGITAL - An ON (high) or OFF (low) voltage pulse. Examples of devices that generate digital signals are: Hood Switch Crankshaft Position Sensor Switch inputs can be power side switched or ground side switched. In other words, power side switched input provides voltage to the control unit when the switch is closed while a ground side switched input provides a ground path when the switch is closed. Advanced Automotive Electrical Systems 25

35 Digital Signal ECU Outputs The ECU operates various components called actuators through three types of outputs. These ECU outputs include: Constant ON or OFF POWER (source) Constant ON or OFF GROUND Pulsed POWER (source) or GROUND The ECU controls either the source voltage or the ground for the load. In most cases, the ground side of the circuit is switched, rather than the source voltage. Examples of actuators found in Nissan and Infiniti systems are motors, relays, solenoids, and bulbs. 26 Advanced Automotive Electrical Systems

36 ECU output voltage, ground and pulse signals can be measured using a Digital Multi-meter or CONSULT-III. While constant voltage and/or ground signals are easily measured and interpreted, voltmeter readings of pulse signals will indicate only the average voltage present. Using the example below of a pulse signal, notice the volt reading that would be displayed on the meter is the average voltage of the pulse signal. To diagnose the operation of the ECU circuits, pulse signal output (and in some cases input) measurements should also include one of the following: Frequency (Hz) Duty Cycle (%) Pulse Width (ms) Frequency A pulse signal is one in which voltage is rapidly switched ON and OFF. Frequency is a measurement of how often something repeats itself or cycles in a specific period of time. A cycle includes voltage ON and OFF and starts when the voltage switches ON and ends when the voltage switches ON again. The FREQUENCY of a pulse signal refers to how many cycles occur Advanced Automotive Electrical Systems 27

37 in 1 second (cycles per second). The unit of measurement for frequency is Hertz, often abbreviated as Hz. Duty Cycle Frequency alone is not sufficient to describe pulse signals. In some cases frequency remains constant, but the length of ON time and OFF time varies. The relative difference between ON time and OFF time is called duty cycle. Duty cycle is measured as a percentage (%). Duty Cycle High is the time when the signal is more positive (12V). Duty Cycle Low is the time when the signal is more negative (0V). Pulse width is similar to duty cycle. While duty cycle is a percentage of ON time in relation to OFF time of the signal, pulse width is an reading of the length of time the signal is on. Typically, pulse width is expressed as milliseconds (thousandths of a second), often abbreviated as ms. 28 Advanced Automotive Electrical Systems

38 To review, pulse signals can be measured in three ways: 1. Frequency is the number of complete ON/OFF cycles per second and is usually measured in Hertz (Hz). 2. Duty Cycle is the length of time a signal is ON compared to the total available time. It is measured as a percentage (%). 3. Pulse Width is the length of time a signal is ON compared to the real time and is usually measured in milliseconds (ms). ECU Diagnosis The ECU provides a good test location when diagnosing symptoms in electronically controlled circuits. Usually, entire circuits can be tested from the ECU. Often, Nissan and Infiniti Service Manuals will provide ECU terminal testing information including expected values and in some cases oscilloscope waveforms. NOTE: Refer to the applicable Service Manual for ECU terminal testing information and precautions. Determine whether the component is a load, an input or an output. If an input, determine the type of signal provided to the ECU. If an output, determine whether the ECU provides power or ground. Leave the control unit wiring harness connected when testing. Carefully back probe the wire terminal with a thin wire or "T" pin being careful not to puncture the insulation. If no load is between the power source and the ECU, battery voltage should be measured at the ECU terminal. If the ECU provides the load's ground, voltage should be nearly zero volts when the load operates. Remember how a circuit operates. Loads use all the available voltage (pressure) to push current through the load. After the last load (on the ground side of the circuit) voltage should be nearly zero volts. For ECU outputs to operate, inputs from sensors must first be processed by the ECU. Outputs are then provided, supplying source or ground so current can flow and the load can operate. The ECU is the processing center for these input signals. However, if an ECU output (LOAD) is inoperative or not operating as expected, always check the quality of the ECU inputs. Remember: GIGO (GARBAGE IN, GARBAGE OUT). Advanced Automotive Electrical Systems 29

39 Depending on the type of signal, ECU inputs and outputs can be measured using: A DVOM (Digital Volt-Ohm-Meter) -For viewing non-switching or slow switching voltages CONSULT-III An Oscilloscope -For viewing input and output signal voltage changes (patterns) A Duty Cycle Meter - Set 'high' for source side switching - Set 'low' for ground side switching A Pulse Duration Meter - Set 'high' for source side switching - Set 'low' for ground side switching Body Control Module The BCM is very similar to other computers in that the computer makes decisions based on a set of inputs and a program in the central processing unit. The BCM controls the operation of various electrical systems on the vehicle. For example the systems controlled by the BCM on the 2009 Altima would include: Power door lock system Remote keyless entry system Power window system Sunroof system Room lamp timer Warning chime system Head lamps, turn signal and hazard warning lamps system BCM Power Supplies and Grounds For the BCM to operate correctly it must have the correct Power supplies and ground circuits. The BCM will have at least one battery power supply and one ignition power supply. The BCM will have at least one ground circuit. The recommended procedure to check the integrity of the ground circuit is to perform a voltage drop test on the ground circuit while the circuit is operating. NOTE: The CONSULT III or a DMM must be used while performing any voltage checks on the BCM circuits. Using a meter with at least 10M Ω internal impedance assures the technician that the meter will not affect the circuit being tested 30 Advanced Automotive Electrical Systems

40 BCM Diagnosis Body control modules use several different methods of communication between the sensors (inputs), the BCM and the outputs. The different types of circuits that you may see are: Voltage signals Frequency Duty cycle Serial data The most common measurements that you will be performing on Body Control Modules and related circuits will be voltage and resistance tests. On some circuits the ESM will ask you to monitor circuit waveforms. This type of measurement can be performed with the CONSULT III oscilloscope or by using a stand-alone Lab scope. Measuring BCM Voltage and Testing BCM Ground Circuits The CONSULT III or a Digital Volt Ohmmeter (DVOM) with at least 10 MÙ internal impedance must be used to test the voltage and ground circuits of the BCM. Using a DVOM with at least 10 MÙ internal impedance will ensure the technician that the meter will not affect the circuit operation. If a problem with the BCM is suspected it is very important that the voltage supply and ground circuits for the BCM be tested. The recommended test for voltage is to test the available voltage at the specified BCM terminals with the circuit live (voltage drop test). The recommended test to verify the integrity of the ground circuit s is a voltage drop test on the ground circuits. Oscilloscope Usage In some cases the ESM will instruct you to check the waveform pattern of a particular circuit. Once viewed, the ESM will provide an example pattern that you can use to compare the pattern observed on the oscilloscope while testing. In other cases an oscilloscope can be a handy diagnostic tool that can be used by the technician to see if there is a signal on a circuit. The oscilloscope can be used to verify a frequency signal, a duty cycle signal or a serial data signal on a circuit. Using an Oscilloscope to Display a Waveform Pattern The hook up for an oscilloscope is the same as a voltmeter. The positive lead of the meter or CONSULT III should be connected to switching side of the circuit. The negative lead should be connected to a good ground. Refer to the instruction manual for the CONSULT III for scaling and channel options. The oscilloscope will display a real time visual value of the monitored signal(s), in voltage and time, critical for accurately inspecting and monitoring electronic inputs and outputs. Advanced Automotive Electrical Systems 31

41 ECU Input Components and Signals ECM, TCM, BCM, IPDM E/R, 4WD, ABS, Instrument Cluster are all examples of ECUs installed on Nissan and Infiniti vehicles. The most common types of inputs to the ECUs are sensor signal inputs or switched inputs.input sensors can be broken down into classifications. They are: Position sensors Temperature sensors Pressure sensors Light sensors Speed sensors NOTE: Although some of the sensors covered in this text are not directly used by the BCM it is important to review and understand the operation of various types of sensors used on Nissan vehicles. Permanent Magnetic Sensors Permanent magnet sensors can be used as position sensors or as speed sensors. Although not used directly by the BCM the Anti-lock Brake/Traction Control Module and the Electronic Control Module will use this input for wheel speed data. The components of a PM sensor are a coil of wire, which is wrapped around a permanent magnet and a signal plate. The permanent magnet speed sensor generates its own voltage signal. The sensor operates on the principle of induction. By rotating the signal plate the intensity of the permanent magnet lines of force increase and decrease. The increase of intensity of the lines of force induces a voltage into the coil of wire. The sensor produces an analog signal (AC voltage). The permanent magnet sensor can be monitored using CONSULT III. The CONSULT III can be used to perform the following operations: - Check for fault codes as well as WSS data - View the position signal wave pattern (using the oscilloscope feature) - Test for resistance and sensor output voltage 32 Advanced Automotive Electrical Systems

42 Active Speed Sensors The active speed sensor is a type of speed sensor that can produce a digital waveform signal. The main components of an active wheel speed sensor are the control unit, an integrated circuit, a sensor rotor and a permanent magnet. The active speed sensor is supplied a voltage and ground from the ABS/TCS module. As the sensor rotor turns the intensity of the magnetic field changes. The electronics within the wheel speed sensor sense the change in magnetic field intensity. The speed sensor electronics sense the changes in intensity and use this change to toggle the voltage signal (from the ABS/TCS module) high and low. As a result the active speed sensor creates a square wave signal. The active speed sensor can be monitored using the CONSULT III. The CONSULT III can be used to perform the following operations: - Check for fault codes - View WSS data in Data Monitor - View the position signal wave pattern (using the oscilloscope feature) - Test for available and signal voltage The Active wheel speed sensor can also be tested with the J45742 wheel speed sensor tester. Potentiometers (position sensors) A potentiometer is a variable resistor type sensor. The most common use of a potentiometer is as a throttle position sensor. A potentiometer uses three (3) wires, one receiving a set voltage (5 volts) from the computer, one connected to ground through the computer and one connected to the computer to measure the signal voltage. In the case of a throttle position sensor, as the accelerator pedal is moved, the signal voltage of the TPS changes. By monitoring the signal voltage of the TPS the computer can determine position. The potentiometer produces an analog voltage signal. Advanced Automotive Electrical Systems 33

43 The potentiometer can be normally be monitored using CONSULT. CONSULT can be used to perform the following operations: - View the potentiometer signal voltage data - Test for feeds, signal voltage and grounds. Temperature Sensors Temperature sensors used on Nissan vehicles are thermistor type sensors. Coolant and air temperature sensors are used to generate signals based on engine coolant and air temperatures. An example of a thermistor that may be used by the BCM is the ambient temperature sensor. The air and temperature sensors used on Nissan vehicles are Negative Temperature Co-efficient Thermistors. This type of resistor changes its resistance value based on temperature. Low temperature produces a high resistance in the sensor while high temperature produces low resistance in the sensor. The control units will supply a reference voltage of 5 volts to the temperature sensor. As a result of the resistance change, as the sensor warms up the voltage drop across the sensor decreases which causes the voltage that is being monitored at the control unit to drop. Most temperature sensors can be monitored using the CONSULT. The CONSULT can be used to perform the following operations: - Check for fault codes as well as Temperature Sensor data - Test for feeds, signal voltage and grounds. Pressure Sensors Pressure sensors are used to measure changes in pressures. Examples of pressure sensors used on Nissan vehicles are manifold pressure sensor, air conditioning pressure sensors and evaporative pressure sensors. The most common type of pressure sensor is a strain gauge. A strain gauge converts a pressure signal into an electrical signal. Pressure applied to a strain gauge type sensor causes a diaphragm inside the senor to deflect. This deflection causes a strain to the gages in the sensor. This strain on the gages causes a change in resistance within the sensor. A change in resistance in the sensor modifies a voltage signal from the control unit. Pressure sensors can be monitored using CONSULT. CONSULT can be used to perform the following operations: - Check for fault codes as well as pressure sensor data - Test for feeds, signal voltage and grounds. Ultra Sonic Sensors Ultrasonic sensors are used in the rear sonar systems on some Nissan vehicles. 34 Advanced Automotive Electrical Systems

44 Ultrasonic Sensors are designed to transmit an ultrasonic signal. This signal is sent out from the sensors installed in the rear bumper. If the signal detects an object the ultrasonic signal is reflected back to the sensor. The rear sonar sensors measure the time from the transmitted signal to the time the signal is reflected back and sends this information to the sonar control unit. Power supply and grounds can be tested. Rear Sonar On-Board diagnosis will record and report fault codes as well as clear stored codes. Light Sensors The auto light control system uses an optical sensor that detects the brightness of outside light. When the lighting switch is in AUTO position, it automatically turns on/off the parking lamps and the head lamps (and fog lamps, if equipped) in accordance with the ambient light. The 2009 Murano also uses a light sensor for the rain sensitive wiper control. Light sensors are used in the operation of automatic head lamp systems. The level of light can be determined by using a photocell. A photocell is a resistor that changes resistance when light strikes its surface, as light strikes the surface, the resistance of the photocell decreases. The decrease in resistance across the photocell changes the amount of voltage drop across the sensor. The computer would monitor the amount of voltage drop and then determine the amount of light intensity. - Power supply and grounds can be tested - Signal voltage can be monitored Switched Inputs Switched inputs circuits consist of a switch, a power supply and a monitor circuit. The most common voltages used are 5 volts and 12 volts. By switching the specific switch off and on the computer will see the voltage signal change from high to low or low to high. In the example below the computer would see a high voltage signal when the switch is open and then a low voltage signal when the switch is closed. Input switch voltages can be normally be monitored using the CONSULT-III. Monitor circuit voltage can be checked with a DMM at the monitor circuit terminal. BCM Outputs The most common type of output device controlled by the BCM is the series reversible electric motor. Examples of series reversible electric motor circuits controlled by the BCM are power window motors, power door lock motors and sunroof motors. Advanced Automotive Electrical Systems 35

45 Motors Most BCM controlled motors are series bi-directional type motors. This means that if the current flow is sent in one direction the armature in the motor will rotate in one direction. Reversing the current flow to the motor will rotate the armature in the motor in the opposite direction. The BCM can reverse the direction of current flow depending on the desired motor direction. Examples of where these types of series reversible motors are used are power window motors, power door lock motors. CONSULT can normally be used to test the operating signals that are sent to motors. A DVOM can be used to test the voltage signals from the BCM as well as CONSULT and an Amp clamp can be used to monitor the amount and direction of current flow through the motor circuit. BCM Controlled Systems In this section of the module we will look at a brief overview of a few BCM controlled systems. They are: Warning chime system Power door lock system Remote keyless Entry System Warning Chime System To activate the warning chime the BCM must see the correct combination of input signals. The warning chime can be turned on by three different vehicle systems. They are: Seat belt warning chime Ignition key warning chime Light warning chime Ignition key warning chime BCM sounds the warning chime when the driver s door is opened with key in ignition key cylinder and ignition switch OFF or ACC position. Light warning chime With the key removed from the ignition switch, the driver door open, and the Lighting switch in 1st or 2nd position, the warning chime will sound. [Except when head lamp battery saver control operates (for 5 minutes after ignition switch is turned to OFF or ACC position) and head lamps do not illuminate. Light warning chime operation To operate the Light warning chime the BCM must see the correct combination of signals from the Combination switch. As well as the above input signals a ground must be seen at terminal # 47 of the BCM. The LH front door switch provides the ground. With these conditions, when power and ground are supplied, the light warning chime sounds. 36 Advanced Automotive Electrical Systems

46 Remote Keyless Entry System (Power door Locks) The Remote Keyless Entry System provides the customer with a remote method to perform the following operations: - Power door lock operation - Turn the interior lamps on - Provides a panic alarm mode - Trunk lid opener - Automatic power window down operation The main components of the keyless entry system are the key fob and the BCM. Depending on the key fob signal the BCM will then command the desired operation. Key Fob A key fob transmits radio signals to the BCM. The BCM will then decode the radio signal and complete the instruction. The key fob can be tested with the Remote Keyless Entry Tester J or with Consult III in the DATA mode selection. Remote Keyless Entry Power Door Lock Operation Door Lock Operation with key fob BCM receives a LOCK signal from key fob. BCM locks all doors with input of LOCK signal from key fob. Door Unlock operation with the key fob When an UNLOCK signal is sent from key fob once, driver's door will be unlocked. Then, if an UNLOCK signal is sent from key fob again within 5 seconds, all other door will be unlocked. Let s look at the steps necessary to unlock and then lock all the doors with the remote keyless entry system. Door Unlock To unlock all the doors the BCM must see 2 unlock signals (within 5 seconds) from the key fob. When the unlock signals are seen the BCM will first send an unlock signal from the BCM door unlock (DR) terminal to the front door (LH) lock actuator. The front door (LH) lock actuator is grounded through the BCM door lock terminal. The BCM will then send an unlock signal out the Door unlock out (AS/RR) BCM terminal. This will send an unlock signal to the passenger and rear door lock/unlock actuators. The passenger and rear door lock actuators are grounded through the same terminal as the driver s door lock/unlock actuator. Door Lock To lock the doors the BCM must see a lock signal from the key fob. When the lock signals are seen the BCM will send a Door lock signal from the Door lock out (all) terminal to the door lock/ unlock actuators. The drivers door lock/unlock actuator will be grounded through the driver s door unlock out terminal. The passenger and the rear door lock/unlock actuators will be grounded through the door unlock out terminal. Advanced Automotive Electrical Systems 37

47 Combination Switches BCM FUNCTION The BCM has a combination switch reading function for reading the operation of combination switches (light, wiper washer, turn signal) in addition to the function for controlling the operation of various electrical components. COMBINATION SWITCH READING FUNCTION The BCM reads the combination switch (light, wiper) position by monitoring input and output signals to the combination switch from the BCM. The BCM then controls various electrical components based on the input and output signals. The BCM can read the information from a maximum of 20 switches by combining five input terminals (INPUT 1-5) and five output terminals (OUTPUT 1-5). Inputs (from the BCM to the combination switch) By continually monitoring the digital voltage patterns at the BCM Input terminals 1-5, the BCM can determine the combination switch position. Depending on the position of the switches in the combination switch, the voltage patterns monitored at INPUT 1-5 are modified and by the activation of the transistors at OUTPUTS 1-5. To monitor the position of the switches in the combination switch the BCM will transmit 2 ms pulse signals simultaneously, from INPUT terminals 1-5 at 10 ms intervals, to the combination switch. The BCM also activates the transistors shown at the OUTPUT terminals sequentially in the order of Turning the transistors on in the BCM will allow the current to flow through any complete circuits through the combination switch. The current flow through the combination switch will either stop at an open switch or be sent through a closed switch to the specific BCM OUTPUT. The BCM then monitors the voltage pulses at the input terminals. 38 Advanced Automotive Electrical Systems

48 Example#1 - Lighting switch first position is turned on When the lighting switch is in the first position, the TAIL LAMP is closed.the circuit between INPUT 4 and OUTPUT 5 is complete. When the transistor at OUTPUT 5 is activated by the CPU the INPUT pulse signal will be grounded for 50 microseconds. This modifies the 2 ms INPUT pulse pattern which is read by the BCM. Advanced Automotive Electrical Systems 39

49 Operation Modes Combination switch reading function has operation modes as follows: Normal status - When the BCM is not in sleep status; INPUT terminals (1-5) each turn ON- OFF every 10 ms. Sleep status - BCM reads the status of the combination switch at 60 ms interval when BCM is controlled at low power consumption mode. Diagnosing the Combination Switch Operation The Combination switch operation sensor can be monitored using CONSULT. CONSULT III can be used to perform the following operations: - Observe the combination switch on/off data - Observe the communication from the combination switch to the BCM with the use of the oscilloscope. The technician may have to check for continuity between the combination switch and the BCM. MULTIPLEXING SYSTEMS Multiplex is defined as; "relating to, having, or consisting of multiple elements or parts" or "relating to or being a system of simultaneous communication of two or more messages on the same wire or radio channel". Nissan and Infiniti vehicles have used multiplexing technology for many years. Multiplexing technology has been an integral part of systems known as: In-Vehicle Multiplex System (IVMS), Local Area Network (LAN) and Control Area Network (CAN) to name a few. What these systems have in common is the ability to send and receive information to multiple control units using Data Lines. These systems were developed to help reduce the number of components and electrical wiring required to operate various systems while reducing cost and vehicle weight. The earliest multiplexing systems used in Nissan vehicles were very simplistic and were generally limited to the power window system. The master unit was a microprocessor located in the driver s door switch. The passenger door switch and both rear door switches contained subprocessors or slave units. When the driver pressed his window switch, the door module closes a control switch (transistor or relay) that provides power to the window motor. If the driver pressed the switch to open or close any of the other windows, the driver's door module sent a packet of data onto the communication bus of the window system. This packet tells a different module to energize one of the power-window motors and which circuit polarity to apply. In this way, most of the signals that leave the driver's door module are consolidated onto the one or two wires that form the communication bus and communication is one-way. 40 Advanced Automotive Electrical Systems

50 Simple Multiplex System Driver s Door Switch (Master) LR Door Switch (Slave) Assist Door Switch (Slave) RR Door Switch (Slave) In-Vehicle Multiplexing System (IVMS) In-Vehicle Multiplexing System (IVMS) was a more sophisticated system used in Nissan and Infiniti between 1994 and IVMS is a type of Local Area Network (LAN) system which uses one or more communication or data lines. This simply means that various devices are wired together so they can communicate with each other, with one device acting as the main control unit. In the IVMS type of LAN system, a main control, such as the Body Control Module, consolidates inputs and outputs for an area of the car. Using a communication bus it can receive signals from local control units, make decisions, and send requests to the local control units to perform certain functions. This type of system can combine the operation of power window, power door lock, remote keyless entry, and theft warning systems into one system. IVMS BCM (BODY CONTROL MODULE) DRIVER S DOOR CONTROL UNIT (LCU01) PASSENGER S DOOR CONTROL UNIT (LCU02) REAR RH DOOR CONTROL UNIT (LCU03) REAR LH DOOR CONTROL UNIT (LCU04) MULTI REMOTE CONTROL UNIT (LCU05) Advanced Automotive Electrical Systems 41

51 Local Area Network (LAN) Systems LAN systems in general are broadcast serial networks comprised of one master unit and up to sixteen slave units. All messages are initiated by the master with, at most, one slave unit responding with a confirmation signal. Some LAN systems were Tx/Rx type with one transmission line and a separate reception line. The master unit sent the command on the transmission data line and the responding slave unit would send a confirmation back on the reception data line. Current Nissan LAN systems utilize one or more communication data lines between master and slave units with transmission and reception occurring on the same line. Currently, Nissan and Infiniti vehicles use LAN systems for HVAC control, and power window and door lock control. LCU (Local Communication LCU (Local M Control Unit) Interface Control Unit) PBR Auto Amp. Air mix door motor Mode door motor Intake door motor Controller Area Network (CAN) Systems Nissan and Infiniti vehicles have advanced rapidly in recent years with more and more computerized controls. This means the vehicles are equipped with numerous electronic control units. Unfortunately, more control units usually results in additional vehicle wiring and weight. The CAN System offers a means for reducing the additional wiring and weight by linking the control units together with common communication lines so information can be shared between control units. Controller Area Network (CAN) is a broadcast serial bus standard for connecting electronic control units. A modern automobile may have as many as 50 electronic control units (ECU) for various subsystems. Typically the biggest processor is the engine control module, which is also referred to as ECM in the context of automobiles; others are used for transmission, air bags, anti-lock braking, cruise control, audio systems, windows, mirror adjustment, etc. Some of these form independent subsystems, but communications among others are essential. A subsystem may need to control actuators or receive feedback from sensors. The CAN standard was devised to fill this need. This type of communications system was developed by Robert Bosch in the 1980s. 42 Advanced Automotive Electrical Systems

52 Nissan first introduced CAN on the 2002 Infiniti Q45 (F50) then the 2002 Nissan Altima (L31). Most Nissan and Infiniti vehicles now have a CAN System. This enabled many major control modules for different systems to share data and eliminate the need for redundant sensors and extra wiring. V-CAN The V-CAN or Vehicle CAN system is the main network used for communication between the engine control module, transmission control module, body control module, etc. Some vehicles also employ an M-CAN or Multimedia CAN system which networks such systems as Audio- Visual, entertainment, navigation, Bluetooth phone, Rear View Camera and IPod. M-CAN may use a different communication protocol or communication speed from V-CAN due to the type of data transmitted. The main module on the M-CAN will also be a component of the V-CAN system. System Description CAN communication is a multiplex communication provided by using a twisted pair of communication lines (wires) to transmit and receive many signals between multiple control units at high speeds. We refer to our communication lines as "CAN H" (High) and "CAN L" (Low). CAN H and CAN L establish a network between the control units for signal communication. Advanced Automotive Electrical Systems 43

53 Conventional System Connection The following drawing illustrates a conventional system connection. CKP Sensor Engine Coolant Temperature Signal Engine Control Module (ECM) Combination Meter Engine Coolant Temp Sensor Throttle Position Sensor Engine Speed Signal Closed Throttle Position Signal Engine Speed Signal A/T Position & Indicator Signal VDC/TCS/ABS Control Unit A/T Control Unit Wheel Speed Sensors Vehicle Speed Signal P/N Position Switch Note that there must be an independent connection between each control unit in order to exchange information. CAN Communication System Connection The drawing below illustrates the system connection using CAN communication. Note the reduction in wiring with the same number of control units. CAN communication enables the sharing of information between all control units. CKP Sensor Engine Control Module (ECM) Combination Meter CAN H Engine Coolant Temp Sensor Throttle Position Sensor CAN L Vehicle Speed Signal, Engine Speed Signal, Engine Coolant Temperature Signal, A/T Position & Indicator Signal, Closed Throttle Position Signal VDC/TCS/ABS Control Unit A/T Control Unit Wheel Speed Sensors P/N Position Switch 44 Advanced Automotive Electrical Systems

54 A Termination Resistance is incorporated into the ECM (Engine Control Module) and the IPDM E/R (Integrated Power Distribution Module Engine/Room). Vehicles not equipped with an IPDM E/R have the termination resistance located in the A/T Control Unit or Instrument Cluster. All CAN Systems have termination resistors, located in control units displayed on either end of the vehicle s CAN System schematic, to verify the integrity of the circuit. DISPLAY C/U Steering angle sensor 120 Ω 120 Ω ECM TCM DLC BCM METER ABS IPDM E/R CAN Diagnosis When diagnosing a CAN System concern, here are a few items to consider: CAN Communication diagnosis in the Service Manual is designed for reproducible faults. The diagnosis is primarily designed to locate opens in the CAN Communication circuit (CAN H and/or CAN L). If more than one control unit has a CAN Communication System DTC (U1000/U1001/ U1010) and one of the control units has "P", "C", or "B" codes, investigate these first before performing CAN System diagnosis. It is most important to select the correct CAN system type for the vehicle and model year of the vehicle CAN system Diagnosis work flow varies from model to model and model year to model year. If you are not familiar refer to the applicable ESM for the correct procedure. Advanced Automotive Electrical Systems 45

55 Diagnostic Trouble Codes for CAN communication errors have specific meanings as with other systems: - U1000 This code is set when communication related to OBDII diagnosis is missing from any control unit for two seconds or more. - U1001 This code is set when communication of non-obdii related data is missing for two seconds or more. - U1002 This code is set when communication of data related to OBDII is missing for less than two seconds. - U1010 Internal failure of the CAN controller circuit in an ECU will cause that ECU to store this code. It may also set U1000 or U1001 in other communicating modules. Multiplexing Issues Multiplex communication is carried out using Binary Digits or Bits, values of either 1 or 0. A byte is a basic unit of measurement of information storage in computer science, which usually consists of eight bits. The transmission rate of this information is measured in bytes per second or BPS. The bits are transmitted serially or one right after the other. Because the bits are arranged in series, transmission can be performed over one wire. Parallel transmission would be much faster, but would require eight wires, one for each bit in the message byte. The CAN systems use high speed transmission in the range of 500 kilobytes per second or 500,000 bytes per second. This communication speed limits the entire length of the CAN system to less than 30 meters. Branch lines from the main lines are limited to less than 1 meter in length. Changes in these specifications would result in communication errors. CAN systems are also limited to the number of communicating devices that share data. Nissan CAN systems can tolerate no more than 16 communication nodes connected to the bus system without the probability of errors being created. The load or rate at which CAN messages occupy the data line cannot exceed 50% without creating errors in the messages. With new technology and advancements in electronic control bus loads will soon exceed the 50% limit. Multiplexing Remedies There are a number of ways to alleviate the issues of bus system overload and accommodate the increasing number of control modules sharing data. Many of these remedies are already appearing in Nissan and Infiniti vehicles. They include: - Local CAN - Multiple CAN systems - CAN Gateway - Local Interconnect Network (LIN) Systems - Universal Asynchronous Receiver/Transmitter (UART) 46 Advanced Automotive Electrical Systems

56 Local CAN Local CAN systems use the same protocols and design standards as V-CAN systems but are used to share data within a specific group of control modules independently of the V-CAN. An example of this design is the VVEL control system used in the 2009 Nissan 370Z, the Infiniti 2008 G37 and FX50. The VVEL control module is responsible specifically for intake valve timing and lift in response to other engine operating conditions controlled by the ECM. The ECM and VVEL control module share data through a local CAN system to optimize camshaft control with other engine management mapping. Another example is the 4 Wheel Active Steering option for the Infiniti G37 Coupe. The 4WAS Main Control Unit and the ABS Control Unit receive data from the V-CAN system for operation. These units also utilize a local CAN system to share signals with the Yaw Rate/Side G Sensor and the 4WAS Front Control Unit. Multiple CAN Systems The Altima Hybrid uses two CAN bus systems for data communication. V-CAN 1 is the CAN system used to communicate data between the ECM, the Hybrid Control Module and non-powertrain control modules. V-CAN 2 is used for data communication between the ECM, the Hybrid Control Module and hybrid powertrain related control modules and sensors. ECM ABS EPS STR Hybrid Control Module V-CAN 2 DLC V-CAN 1 DCU I-KEY METER ABS IPDM CAN Gateway CAN Gateway was introduced with the 2009 Infiniti FX35/50. The gateway system communicates between two separate V-CAN systems. This system selects and transmits only necessary information from one V-CAN to the other. The current CAN gateway must be configured at installation to match the equipment and systems present in the vehicle. The configuration must be performed using CONSULT-III in a process similar to BCM Configuration. The current configuration of the original gateway may be read by CONSULT-III when possible, and written to the replacement gateway. If the read func- Advanced Automotive Electrical Systems 47

57 tion is not possible a manual configuration procedure must be used. Local Interconnect Network (LIN) System The LIN bus (Local Interconnect Network) is a vehicle bus standard used in conjunction with other automotive network architectures. The LIN is a small slower speed network system that is used as a sub-network of a CAN bus to integrate intelligent sensors or actuators with system controllers. The benefit of using LIN bus is the relative cost as compared to CAN bus. LIN systems are less expensive to produce and can still satisfy the requirements for the system control. An example of a LIN bus system is the HVAC system used in Nissan Armadas, Titans and Infiniti QX56. The LIN bus is a single wire communication network between the A/C Auto Amplifier and the Rear Air Control (Front) and the Rear Air Control (Rear). Universal Asynchronous Receiver/Transmitter (UART) Some microprocessors require data in parallel format. Serial transmission of digital information through a single wire is much more cost effective than parallel transmission. A Universal Asynchronous Receiver/Transmitter (UART) is used to convert the transmitted information between its serial and parallel forms at each end of the communication line. A UART can be an individual circuit or part of an integrated circuit depending on the system design requirements. In Nissan and Infiniti vehicles they are used for serial data transmission between the power window switches and the BCM or the Remote Keyless Entry Receiver and the BCM for example. UARTS are used between the Unified Meter and the Meter and A/C Amp on some of our vehicles as well. 48 Advanced Automotive Electrical Systems