ASE 8 - Engine Performance. Module 8 Ignition Systems Triggering

Transcription

1 Module 8 Ignition

2 Acknowledgements General Motors, the IAGMASEP Association Board of Directors, and Raytheon Professional Services, GM's training partner for GM's Service Technical College wish to thank all of the people who contributed to the GM ASEP/BSEP curriculum development project This project would not have been possible without the tireless efforts of many people. We acknowledge: The IAGMASEP Association members for agreeing to tackle this large project to create the curriculum for the GM ASEP/BSEP schools. The IAGMASEP Curriculum team for leading the members to a single vision and implementation. Direct contributors within Raytheon Professional Services for their support of translating a good idea into reality. Specifically, we thank: Chris Mason and Vince Williams, for their leadership, guidance, and support. Media and Graphics department under Mary McClain and in particular, Cheryl Squicciarini, Diana Pajewski, Lesley McCowey, Jeremy Pawelek, & Nancy DeSantis. For their help on the Engine curriculum volume, Subject Matter Experts, John Beggs and Stephen Scrivner, for their wealth of knowledge. Finally, we wish to recognize the individual instructors and staffs of the GM ASEP/BSEP Colleges for their contribution for reformatting existing General Motors training material, adding critical technical content and the sharing of their expertise in the GM product. Separate committees worked on each of the eight curriculum areas. For the work on this volume, we thank the members of the Engine committee: Jamie Decato, New Hampshire Community Technical College Lorenza Dickerson, J. Sargeant Reynolds Community College Marvin Johnson, Brookhaven College Jeff Rehkopf, Florida Community College at Jacksonville David Rodriguez, College of Southern Idaho Paul Tucker, Brookdale Community College Kelly Smith, University of Alaska Ray Winiecki, Oklahoma State University - Okmulgee

3 Contents Module 8 Ignition Acknowledgements... 2 Introduction... 6 Hall Effect Opti-Spark Magneto-Resistive Sensor Crankshaft Position Sensor (CKP) Camshaft Position Sensor (CMP) Sensing Decode Mode CKP Sensor Variation Learn Process L Ignition System Triggering GEN III Coil-Near-Plug Ignition System Triggering Other GM Ignition Triggering Systems Compression Sense Ignition System Triggering Distributor Ignition System Triggering... 42

4 NATEF Tasks 1. Diagnose ignition system related problems such as no-starting, hard starting, engine misfire, poor driveability, spark knock, power loss, poor mileage, and emissions concerns on vehicles with electronic ignition (distributorless) systems; determine necessary action. 2. Diagnose ignition system related problems such as no-starting, hard starting, engine misfire, poor driveability, spark knock, power loss, poor mileage, and emissions concerns on vehicles with distributor ignition (DI) systems; determine necessary action. 3. Inspect and test ignition primary circuit wiring and solid state components; perform necessary action. 4. Inspect and test ignition system secondary circuit wiring and components; perform necessary action. 5. Inspect and test ignition coil(s); perform necessary action. 6. Check and adjust ignition system timing and timing advance/retard (where applicable). 7. Inspect and test ignition system pick-up sensor or triggering devices; perform necessary action GM STC Tasks 1. Identify the basic components of the ignition system 2. Describe the basic operation of the ignition system 3. Describe the operation of the ignition module 4. Describe the operation of the IC circuit 5. Describe the operation of the CKP sensor 6. Identify the PCM inputs used for the ignition system control 7. Describe the PCM outputs used for ignition control 8. Identify the ignition components 9. Identify ignition components differences between vehicle lines 10.Identify the components of the C3I 11. Describe the operation of the C3I 12.Identify the components of the DIS 13. Describe the operation of the DIS 14. Identify the components of the HVS 15.Describe the operation of the HVS 16. Consult service information and interpret data 8-4

5 17.Demonstrate use of the Tech 2 18.Interpret data related to Tech 2 usage 19.Demonstrate the ability to use a DVOM and interpret data 20.Diagnose electrical circuit concerns 21. Follow service information and interpret data 22.Demonstrate the ability to follow DTC codes and interpret data 23.Follow vehicle service schematics and interpret data 24. Demonstrate knowledge of the OBDII system 25. Follow OBDII diagnosis charts and interpret data 26.Demonstrate operational knowledge of vehicle fuel systems 27. Diagnose concerns related to vehicle fuel systems 28. Demonstrate operational knowledge of vehicle ignition systems 29. Diagnose concerns related to vehicle ignition systems 8-5

6 Introduction Regardless of the type, all ignition systems are made up of three sections or sub-groups; Primary, Triggering, and Secondary. Figure 8-1, Ignition Systems 8-6

7 The primary section of the ignition system includes all of the components and wires operating on low voltage 12 volts or system voltage. The primary circuit includes the ignition switch, coil primary windings, a switching device ignition module, and all associated wires and connectors. Figure 8-2, Primary Circuit All ignition systems require a circuit to turn the current flow on and off in the primary winding of the ignition coil. In the electronic ignition systems used today, this is accomplished by a transistor in the ignition module. The triggering section is considered to be any form of signal that will provide an input to the ignition module, or PCM, for switching of the coil. There are four categories of triggering devices: the Permanent Magnet (PM) Generator (also known as a Variable Reluctance Sensor), the Hall Effect Switch, Optical Pickup, and Magneto Resistive (MR). Ignition systems using each type of these devices will be covered in detail in this section. 8-7

8 The Permanent Magnet, or PM, Generator, also known as a variable reluctant sensor, uses the principle of induction to develop an AC signal. In the sensor, a wire is coiled around a permanent magnet. By rotating a reluctor, which has notches cut into it at precise locations, the magnetic field moves back and forth across the wire winding. This produces an AC voltage signal in the wire. The ends of the wires are connected to either the Ignition Control Module, or ICM, or to the PCM. The signal is converted to the ON/OFF reference and used as the base triggering for the primary circuit. Figure 8-3, Permanent Magnet Generator 8-8

9 For the Crankshaft Position Sensor to work, it must have a fiftythousandths of an inch, plus or minus twenty-thousandths, of an air gap between the sensor and the reluctor. On Electronic Ignition, or EI systems, the sensor is mounted in the block or front cover and is non-adjustable. Figure 8-4, Electronic Ignition On vehicles with Distributor Ignition, or DI system, the pickup coil operates similarly. A magnet field increases and decreases as the teeth of the timer core and pole piece move in and out of alignment. This induces an AC flow through the pickup coil, which is the triggering signal to the ICM. Figure 8-5, Distributor Ignition 8-9

10 EI Systems use a PM Generator and a reluctor that are part of the Crankshaft. The design of the Crankshaft reluctor is an important consideration when diagnosing these systems. Crankshaft reluctors on most four and six-cylinder engines have seven notches. Each sends voltage signals to the ignition module for every revolution of the Crankshaft. Six of the notches are equally spaced at sixty-degree intervals around the Crankshaft. The seventh is positioned ten degrees from the sixth notch. The signal from the seventh or "sync" notch synchronizes the coil firing sequence with Crankshaft position. On four-cylinder engines, the ignition module is programmed to recognize the "sync" notch, count notch number one, and accept notch number two as the signal to fire the 2-3 companion cylinders. Next, the module counts notches three and four, then accepts the number five notch signal as the signal to fire the 1-4 cylinder pair. The sixth and seventh notches are then counted and the process begins again. Note that the coil pack for the second cylinder in the firing order always fires first during start up. On sixty-degree V6 engines, the Module skips the number one notch after the sync signal and fires the 2-5 cylinders on the signal from notch 2. Notch 3 is skipped and notch 4 fires the 3-6 cylinder pair. Finally, notch 6 is used to fire the 1-4 pair. Figure 8-6, Crankshaft Reluctor 8-10

11 PM Generator output voltage varies with engine speed. Typical values range from approximately five-hundred millivolts at cranking speeds to one-hundred volts at high RPM, depending on the application. When measuring the output from a magnetic crank sensor, the voltmeter should be set on an appropriate AC scale. The output from a P M Generator and a given engine, will vary based upon: Cranking speed, The air gap of the sensor to the reluctor, The resistance of the sensor windings, The temperature of the sensor, and The strength of the magnet. Figure 8-7, P-M Generator It is also important to know if the circuit you are diagnosing is a Pull-Up circuit or a Pull-Down circuit, especially in an ignition system. Always refer to the appropriate service information electrical schematics when performing diagnosis on ignition systems. 8-11

12 A Pull-Up circuit has a power source outside the PCM. The PCM does not provide the reference voltage signal. When the switch is closed, external source voltage provides a high reference signal to the PCM. An open switch, on the other hand, provides a low reference signal. Figure 8-8, Pull-Up Circuit A Pull-Down circuit is provided with a reference voltage signal from the PCM. The power source for the circuit is internal to the PCM. When the switch is closed, source voltage is pulled low to an external ground. The PCM registers a low voltage reference signal. When the switch is open, the PCM registers a high reference signal. Figure 8-9, Pull-Down Circuit 8-12

13 Hall Effect Now let's look at another ignition triggering device, the Hall Effect switch. The Hall Effect Switch is used on several ignition system applications. The Hall Effect Switch is an electronic device that produces a voltage signal controlled by the presence or absence of a magnetic field in an electronic circuit. When a magnetic field is introduced perpendicular to a current flowing through a semiconductor, a measurable voltage is induced at the sides of the semiconductor, at right angles to the main current flow. This is known as the Hall Effect. A regulated signal voltage from the ignition module is passed through a semiconductor wafer in the Hall Switch. A permanent magnet mounted beside the semiconductor induces Hall voltage across the semiconductor. The crank sensor is positioned so that metal blades, or "vanes", of an interrupter ring mounted on the crankshaft harmonic balancer damper pass between the semiconductor and the permanent magnet. The Hall voltage is amplified and routed to the base of a transistor, which controls the ground on the signal voltage from the ignition module. Figure 8-10, The Hall Effect Switch When the metal vane is outside the sensor, the transistor is ON and the signal from the module is grounded. 8-13

14 Figure 8-11, When a metal vane comes between the magnet and the semiconductor, the magnetic field is interrupted and the Hall voltage drops off. The Hall voltage drops when the vane is inside the sensor, and the transistor turns OFF and the signal returns to the high state. As the interrupter rotates, signal voltage alternates between high and low states, generating a square-wave with the same pattern as on the interrupter vanes. Note that the module supply voltage is pulled low by the sensor. 8-14

15 Opti-Spark Now let's look at a triggering system based on the use of an optical pickup. This was first used in 1992 on the second generation small block V8 engines, specifically the LT 1 five point seven liter found in Corvettes and later in other applications. The ignition system that uses the optical pick-up sensor is called Opti- Spark. Opti-Spark is a distributor ignition system that consists of the following components: The Distributor Housing A Cap and Rotor The Optical Position Sensor A Sensor Disk The Pickup Assembly The Distributor Drive Shaft Figure 8-12, Opti-Spark 8-15

16 The Pick-Up is part of the distributor assembly that is located on the front of the engine and is driven directly by the camshaft. The Optical Pick-Up System provides actual crankshaft position in degrees to the PCM. This is possible by using a flat disk with two rows of notches cut around its circumference. Figure 8-13, Optical Pick-Up System One row has three hundred and sixty notches, each one degree wide. The other row has eight notches. These eight notches are arranged with the following widths: 2 degree, 7 degree 2 degree, 12 degree 2 degree, 17 degree 2 degree, 22 degree The Optical sensor uses an infrared light source and receiver. 8-16

17 When the camshaft turns, the Optical Pick-Up produces two digital signals. The 360 notches produce a high-resolution signal, while the 8 notches produce a low-resolution signal. Figure 8-14, Optical Pick-Up Signal Both signals are sent directly to the PCM; therefore, this is an upintegrated system with no bypass mode. The low-resolution signal is used for RPM reference. Without the lowresolution signal, there is no spark or fuel delivery. The high-resolution signal is used to fine-tune the engine's timing, especially at higher RPMs. The engine will start and run without the high-resolution signal, but a long crank complaint, along with reduced performance, could be noticed. The engine will not run without the low-resolution signal present. 8-17

18 Magneto-Resistive Sensor A Magneto-Resistive, or MR, Crankshaft Position Sensor is used on some General Motor trucks. This sensor generates a digital signal. The MR Sensor is similar in operation to a Hall Effect Switch. Both sensors require a magnetic field to operate, have three wires and produce a digital output signal. A permanent magnet is located inside the sensor end nearest the Crankshaft Reluctor Wheel. Figure 8-15, Magneto-Resistive Sensor 8-18

19 The magnet is positioned between two magnetic reluctance pick ups, MR1 and MR2. The magnetic field changes in the area of MR1 and MR2 as the Reluctor Wheel passes. Each tooth of the Reluctor Wheel reaches MR 1 before MR2. Both MR1 and MR2 produce identical voltage signals, but the MR2 signal is just a fraction of a second later than the MR1 signal because of its location to the approaching Reluctor Wheel. Figure 8-16, MR1/MR2 Voltage Signals Both the Crankshaft Position Sensor and Reluctor Wheel should be handled carefully. Any dents or other imperfections in the wheel can cause excessive Crankshaft Position sensor noise. A damaged Reluctor Wheel or Crankshaft Position Sensor may cause improper operation of on-board diagnostics, such as the misfire diagnostics. Signals from MR and MR2 cause a differential amplifier to produce the MR differential output. This signal is used to switch a Schmidt Trigger on and off. A Schmidt trigger is a two-state device used to square-up waveforms with slow rise and fall times. Digital circuits prefer wave forms with fast rise and fall times, and uneven waveforms can distort data if fed directly into a digital circuit. The Schmidt trigger converts these erratic signals into square waves. The sensor output is then like that of a Hall Effect Switch. One difference from most Hall Effect Switches is that the VCM does not supply a pulled up signal wire for the sensor to toggle to ground. Instead, the MR sensor pulls the signal up to five volts and toggles it to ground. 8-19

20 Crankshaft Position Sensor (CKP) The three point five liter LX5 engine uses a single crankshaft position, or CKP, sensor located in the left side of the engine block behind the starter motor. The air gap between the CKP and the reluctor wheel is not adjustable. Figure 8-17, Crankshaft Position Sensor (CKP) The CKP sensor operates on the Magneto-Resistive principle and is actually two sensors within a single housing. The sensors are called CKP Sensor A and CKP Sensor B. Figure 8-18, CKP Sensor A and B The CKP sensor connector contains six terminals to provide power, reference low, and signal circuit connections between the PCM and the CKP Sensors A and B. Figure 8-19, CKP Sensor Connector 8-20

21 The four point six liter L D 8/L 37 engines use two separate CKP sensors. The CKP sensors operate on the Magneto- Resistive principle. The sensors are called CKP A and CKP B. They are located in the left side of the engine block and have a non-adjustable air gap. Figure 8-20, CKP A and CKP B Sensors The CKP connectors are keyed to prevent plugging the CKP harness connector into the wrong sensor. However, nothing prevents a technician from installing the CKP sensors into the wrong holes. Because the CKP sensors have angled ends, improper installation will result in damage to the CKP sensor. Do not over torque the CKP sensors or damage will occur. The PCM can use two different modes of decoding crankshaft position sensor pulses. During normal operation, it performs an angle-based decode operation using both signals. Figure 8-21, Crankshaft Position Sensor Pulses 8-21

22 The engine will continue to operate even if one signal is lost. If this happens, the PCM will use a time-based decode mode. The two sensors, reading the reluctor wheel in the crankshaft, allow the PCM to perform an angle-based decode operation. This is considered a self-clocked system, where one sensor acts as a clock and the other is a data signal. The advantage of angle-based decoding is the increased accuracy and consistency of signals, even during engine acceleration and deceleration. If one sensor is not operating correctly, the PCM will use a time-based decode operation. A time-based decode operation will read the pulse width of one signal. Since no clock signal is available, time-based decoding is not as accurate during engine acceleration and deceleration. Camshaft Position Sensor (CMP) The camshaft position, or CMP, sensor is used as an input to the PCM to synchronize the ignition system and fuel injectors. The CMP sensor is also used in the misfire detection diagnostic. The CMP sensor operates on the Magneto-Resistive, or MR, principle, and outputs a five volt digital signal to the PCM. The PCM has the ability to sense cam position with the "key-on," engine off. The camshaft reluctor wheel works the same as the crankshaft reluctor wheel. The CMP sensor signal, when combined with the CKP sensor signal, enables the PCM to determine exactly which cylinder is on the firing stroke. Figure 8-22, Camshaft Position Sensor 8-22

23 The CMP sensor signal is toggled by the track on the cam sprocket/ reluctor wheel. Figure 8-23, CMP Sensor Reluctor Track Using the CMP and the CKP sensors, the PCM can determine engine position in six CKP sensor pulses, within ninety degrees. If the CMP signal is absent during engine cranking, there is a fifty percent chance of it starting immediately. The CKP sensor will indicate which two cylinders are at top dead center, but the PCM does not know which cylinder is on the compression and which one is on the exhaust stroke. The PCM will fire one of the cylinders. If an increase in RPM is detected, the correct cylinder was fired and the engine will run. If the correct cylinder was not fired on the first attempt, cranking time will be longer than normal. The three point five liter, LX5 CKP Sensors A and B have separate power, ground, and signal circuits. Figure 8-24, LX5 CKP Sensors A and B 8-23

24 The PCM supplies twelve volts and the ground path for both CKP sensors. These power and ground circuits are also connected to the CMP sensor. Two separate signal circuits connect the CKP sensor and the PCM. One separate signal circuit from the camshaft position sensor provides input to the PCM. Figure 8-25, CKP Sensor and PCM Signal Circuits The four point six liter LD 8/L 37 CKP Sensor A, CKP Sensor B, and the CMP Sensor have separate power, ground, and signal circuits. The PCM supplies twelve volts, ground path and signal circuit for all three sensors. Sensing Decode Mode If a technician believes that the crank sensor input is the cause of a driveability concern, even though no DTC may be set, the technician can switch from the use of both sensors in Angle-based decoding to the use of a specific sensor. Time A is for sensor A and Time B for sensor B. Figure 8-26, Sensing Decode Mode 8-24

25 This eliminates the suspect sensor signal from the PCM for that ignition cycle. In the CKP decode mode the test can be run only one time per ignition cycle. In this mode the CKP Sensor Status data parameter displays the actual PCM operating mode. Figure 8-27, CKP Sensor Status Data Parameter The PCM's 24 X crank sensor data must read "0" before making a command. This is accomplished with the engine not running. All DTCs must be cleared at this time. Keep in mind that even if the Tech 2 is disconnected, the PCM will retain the command state for the entire key cycle. 8-25

26 To begin the decode mode test, choose Powertrain Special Functions, Engine Output Controls, then Crank Position Sensing Decode Mode. Figure 8-28, Decode Mode Test Figure 8-29, State Soft Key Press the select state soft key until the desired state is displayed: time A, time B, or Angle. For this example, time A was chosen. Before starting the engine, press the command state soft key. Start the engine and monitor the CKP sensor status data parameter. Confirm that the CKP sensor status matches what you just selected. If the driveability concern is no longer present while performing this test, CKP Sensor B has a fault. 8-26

27 CKP Sensor Variation Learn Process The CKP Sensor Variation Learn Procedure eliminates unwanted misfire DTCs caused by tolerances in crank sensing components. CKP Sensor Variation Learn Procedure needs to be performed if the Diagnostic Trouble Code P1336 is set, or when replacing the PCM, engine crankshaft, or CKP Sensor. Figure 8-30, Diagnostic Trouble Code P1336 The following steps are used when performing the CKP Sensor Variation Learn Procedure. To prevent personal injury to you and others, begin the CKP Sensor Variation Learn Procedure by: Closing the hood, Setting the parking brake, and Blocking the drive wheels. Once the safety steps have been completed, allow the engine to run until it reaches operating temperature, then turn off the engine, and turn the key to run. Next, select and enable the CKP Sensor System Variation Learn Procedure from the Tech 2, and start the engine. At this time, you'll apply the brake pedal firmly. When the transaxle is in park, rapidly increase accelerator pedal position until it reaches the fuel cutoff. The CKP Sensor Variation compensating values are learned while the engine RPM lowers to an idle. Observe the DTC status for DTC P1336. If the Scan tool indicates DTC P1336 the system variation has not been learned, and the Variation Learn Procedure MUST be performed. The Scan Tool CKP Sensor Variation Learn Procedure will be inhibited if coolant temperature is less than one-hundred fifty eight degrees Fahrenheit or seventy degrees Celsius. Allow the engine to run until it reaches operating temperature. The Variation Learn Procedure will also be inhibited, if any Powertrain DTCs are set before or during the CKP Procedure. Serious engine damage may occur if the throttle is not released as soon as fuel cutoff is reached. When the CKP Sensor Variation Learn Procedure is complete, the PCM has learned sufficient data to prevent unwanted misfire DTCs from setting due to tolerances in crank sensing components. 8-27

28 4.2L Ignition System Triggering The four point two liter ignition system is a coil-per-plug system that is controlled by the PCM There are some differences between the four point two coil per plug system and others. Figure 8-31, 4.2L Ignition System Triggering The CKP sensor in this system is a permanent magnet generator, known as a variable reluctance sensor. The magnetic field is altered by a crankshaft mounted reluctor wheel that has seven machined slots, six of which are equally spaced sixty degrees apart. The seventh slot is spaced ten degrees after one of the sixty degree slots, and is the sync pulse. The CKP sensor signal is received by the PCM. This CMP sensor is triggered by a notched reluctor wheel built into the exhaust camshaft sprocket. The CMP sensor provides six signal pulses every camshaft revolution. Figure 8-32, CMP Sensor Each notch or feature of the reluctor wheel is of a different size for individual cylinder identification. This means the CMP and CKP signals are pulse width encoded to enable the PCM to constantly monitor their relationship. This relationship is used to determine camshaft actuator position and control it's phasing at the correct value. The PCM also uses this signal to identify the compression stroke of each cylinder, and for sequential fuel injection. 8-28

29 GEN III Coil-Near-Plug Ignition System Triggering The Gen 3 V-8 small block engines use a coilnear-plug ignition system. This system consists of 8 coil module driver assemblies, located on the valve covers, which are attached to the spark plugs with spark plug wires. This engine uses a Camshaft Position Sensor, and a Crankshaft Position Sensor. Ignition timing is dependent on both the CMP sensor and the CKP Sensor. While the crankshaft position sensor identifies cylinder pairs at top dead center, the CMP sensor identifies the cylinder stroke, either compression or exhaust. Figure 8-33, GEN III Coil-Near-Plug Ignition System The PCM uses the Camshaft Position Sensor information to determine whether a cylinder is on a firing or exhaust stroke. A1 X reluctor wheel, machined as part of the camshaft, interrupts a magnetic field produced by a magnet within the CMP sensor as the camshaft rotates. Figure 8-34, A1 X Reluctor Wheel The CMP sensor's internal circuitry detects this and produces a signal that the PCM reads. The 24 X Crankshaft Position Sensor CKP Sensor is the most critical input for the ignition system. If the sensor is damaged so that pulses are not generated, the engine will not start. Figure 8-35, 24 X Crankshaft Position Sensor 8-29

30 CKP sensor to Reluctor clearance is also very important. The sensor must not contact the rotating reluctor ring at any time, or sensor damage will result. The CKP sensor is found on the right lower rear of the engine block, behind the starter. The sensor reads a reluctor wheel on the crankshaft to identify cylinder pairs at top dead center. Figure 8-36, CKP Reluctor Wheel The CKP reluctor wheel uses twenty four notches of two different widths, positioned every fifteen degrees. This pulse width encoded pattern allows piston position identification within ninety degrees of crank rotation. The reluctor is heated, indexed, and pressed onto the crankshaft during manufacture. The reluctor must be serviced along with the crankshaft. 8-30

31 Other GM Ignition Triggering Systems Let's look at how the 4.0 and 4.6 liter Direct Ignition System is triggered. The four point oh and four point six liter V 8 Direct Ignition System is a waste spark system that has dual variable reluctance crankshaft sensors, with one reluctor ring to monitor crankshaft position. The reluctor ring has twenty-four evenly spaced notches and eight unevenly spaced notches. Figure 8-37, Direct Ignition System With the "B" sensor mounted twenty-seven degrees of crankshaft revolution behind the "A" sensor, a unique pattern of pulses is created that allows the ignition to synchronize and fire the first coil in less than one half or one hundred eighty degrees crankshaft revolution. The Ignition Module accomplishes this by monitoring the pulses it receives from each Crankshaft Position Sensor. The Ignition Module counts the number of "B" pulses between "A" pulses. The pattern on the reluctor ring allows either zero, one or two "B's "between "A's." When the Module recognizes one or four patterns of B's between A's, the Crankshaft Position is known and the ignition system is synchronized. The ignition can synchronize at four different crankshaft positions; therefore, the first cylinder fired at engine start-up will depend on where or what position the engine stopped at previous Key OFF. The system also uses a magnetic Camshaft Position Sensor for fuel control and misfire diagnostics. Now let's look the triggering system used on GM (C3I ) equipped vehicles, found on the 3.0 and 3.8 liter engines. 8-31

32 This system has Hall Effect switches for crank and cam position with a crank sensor interrupter ring mounted on the back side of the harmonic balancer. In addition, there is an ignition module and a coil pack assembly. Figure 8-38, Coil Packs There are two coil pack designs, Type 1 and Type 2, which are interchangeable on some models. A variation to this system, known as the Fast Start, uses a unique interrupter ring, which gives more precise crank information. This system provides faster starts by supplying information for correct cylinder firing without relying on the cam signal. The CKP sensor on the 3.0 liter engine is located adjacent to the crankshaft harmonic damper. 8-32

33 Two concentric rings on the back of the damper pass on each side of the Hall Effect magnet. The inner ring has three evenly spaced vanes and windows, which send identically timed signals of the same duration. The outer ring has only one window. This single pulse acts as the synchronize signal to set up the logic for triggering the correct ignition coil. Figure 8-39, On the three point eight liter SFI and SFI turbo engines, the synchronize signal is determined by a separate camshaft sensor. The magnet is mounted in the camshaft sprocket. The cam sensor signal identifies cylinder sequence for injector firing on a sequential fuel injector system as well as the sync signal for the ignition module. 8-33

34 The C3 I Fast Start system on the thirty-eight-hundred and 1993 thirtythree-hundred engines use a dual crankshaft sensor and a separate cam sensor. Advantages of the Fast Start system are: faster start-up, walk-home protection in the event of cam sensor malfunction, and more precise measurement of crankshaft sensor signals. Figure 8-40, C31 Fast Start System On Fast Start systems, the dual crank sensor is mounted on the front of the engine beside the harmonic balancer, crankshaft pulley. The CMP sensor is mounted on the timing cover beside the cam sprocket. The arrangement of the interrupter rings on the harmonic balancer is different than on the other V 6 engines. The outside ring has eighteen evenly sized and evenly spaced interrupter blades to produce eighteen pulses per crankshaft revolution. These pulses are known as the 18 X signal. The inside ring has three interrupter blades with gaps, or windows, of 10, 20, and 30 degrees. These gaps, in turn, are spaced 100, 90, and 100 degrees apart respectively. These pulses are referred to as the 3 X signal. With this interrupter ring arrangement, the ignition module can identify the proper cylinder pair to fire within as little as one-hundred-twenty degrees of crankshaft rotation. The module can also fire any cylinder pair reaching TDC first without waiting for the cam or sync signal. 8-34

35 For Crankshaft Sensor Adjustment on the 3300 and 3800 V6s, use adjusting tool part number J to ensure accurate positioning of the sensor, and to maintain proper clearance between the interrupter vanes and the sensor. Figure 8-41, Crankshaft Sensor Adjustment The tool is also used to check interrupter rings for out-of-round. Be sure to follow the procedures listed in current maintenance information when using adjusting tool J The tool can be used to adjust all crankshaft sensors, with the exception of the Delco single-slot design sensor and late model thirty-eighthundreds. The single slot design crankshaft sensors are adjusted using the Kent- Moore feeler gage style adjusting tool, J Figure 8-42, Single Slot Crankshaft Sensors 8-35

36 The and 3400 Ignition System is a hybrid ignition system that uses two crankshaft position sensors. The 24 X Hall switch CKP signal is a direct input to the PCM, while the 7 X, a permanent magnet style CKP signal, is an input to the Ignition Control Module. Figure 8-43, 3100 & 3400 Ignition System The ignition control module sends a 3 X signal to the PCM. The 3 X signal is a condition signal sent by the Ignition Control Module based on the 7 X CKP signal. Below 1200 RPM, the PCM controls ignition timing and idle speed using the CKP 24 X signal. The PCM uses the 3 X signal from the Ignition Control Module to calculate engine speed and crankshaft position over 1200 RPM. If the PCM receives no pulses on this circuit, DTC P1374 sets and the PCM uses the 24 X reference signal circuit for fuel and ignition control. Figure 8-44, 8-36

37 The CMP sensor sends a cam position signal to the PCM, which uses it as a sync pulse to trigger the injectors in proper sequence. The PCM uses the CMP signal to indicate the position of the number one piston during its intake stroke. This allows the PCM to calculate a true sequential fuel injection mode of operation. If the PCM detects an incorrect CMP signal while the engine is running, DTC P0341 sets. If the CMP signal is lost while the engine is running, the fuel injection system shifts to a calculated sequential fuel injection mode based Figure 8-45, on the last fuel injection pulse and the engine continues to run. The engine can be restarted and run in a calculated sequential mode as long as the fault is present with a 1 in 6 chance of injector sequence being correct. Compression Sense Ignition System Triggering The two point two liter engine, RPO code L 61, uses a waste spark electronic ignition system. Figure 8-46, 8-37

38 Although waste spark ignition is familiar technology, the L 61 ignition system is referred to as the Compression Sense Ignition, or CSI. CSI enables the PCM to determine proper engine phasing without the use of a separate camshaft position sensor. CSI's modular design is similar to the ignition systems used on the premium V 6 and V 8 engines. Both systems house nearly all the major ignition system components in a single cassette, although only the L 61 engine uses compression sense. The ignition cassette is mounted directly over the spark plugs, requiring only a connector spring and insulating boot to transfer the ignition energy to the spark plugs. The cassette houses two ignition coils. Each coil sends ignition energy to two paired cylinders at the same time, one cylinder on its exhaust stroke and the other cylinder on its compression stroke. Cylinders 1 and 4 are paired on one coil and cylinders 2 and 3 on the other. One spark plug in each pair always fires from the center electrode to the side electrode. The other always fires from the side electrode to the center electrode. One cylinder's firing voltage rises in a negative direction, relative to engine ground on the way to its final breakdown voltage. It then quickly breaks over in a positive direction back toward ground until the spark line is established. The other cylinder's firing voltage rises in a positive direction, relative to engine ground, then quickly breaks over in a negative direction back toward engine ground until the spark line is established. The polarity characteristics of the spark events are one part of the information reflected in the CSI signal. At the moment an ignition coil fires, a growing voltage potential is created across the gap of both plugs. After about 10 microseconds, the voltage reaches each plug's breakdown voltage level. Breakdown is the point at which the air gap ionizes and conducts current, causing the spark to occur. The breakdown voltage level is determined in part by the pressure within the cylinder. More voltage is required at a higher cylinder pressure. A cylinder on its exhaust stroke has less in-cylinder pressure than a cylinder on its compression stroke. Because of these uneven pressures, the spark plug of the cylinder on its exhaust stroke will break down first by a few microseconds, and will spark first. The order of the spark plug gap breakdown events for the paired cylinders is yet another characteristic that is reflected in the CSI signal. 8-38

39 This ignition system utilizes a unique Compression Sense Ignition sensor to detect the polarity events and the breakdown events in the secondary ignition circuits of each pair of cylinders. This is accomplished by creating virtual capacitors between the secondary coils and the E I module's electronics. One side of these capacitor plates is connected to the ignition secondary outputs. The other side is connected to a resistor network. As current flows on the capacitor plates, a voltage is created on the resistor. The voltage pattern measured across this resistor is what makes up the information in the CSI signal. Figure 8-47, The resistor network allows only the high frequency edge of the plug gap breakdown voltage to pass through for measurement. Cylinders fire in pairs, and from the earlier study on polarity, we know that the voltage of one plug moves toward positive while its pair moves toward negative. And from the breakdown discussion, the plug in the cylinder on the exhaust stroke fires slightly before the one on the compression stroke. These relationships can be seen in the accompanying chart. Figure 8-48, The CSI signal will reflect the polarity and timing of each cylinder's spark plug breakdown voltage event. 8-39

40 Now that we have seen all the various pieces of information contained in the CSI signal, as well as the method in which it is acquired, lets pull it all together and see how it is processed. The E I module houses the CSI input signal logic electronics called the Compression Sense Time Out, or CSTO chip. The CSTO electronics are responsible for interpreting the CSI input signal and creating a 5V square wave output called a camout signal. Figure 8-49, CSTO Chip Logic Here's how the CSTO chip logic works. The first EST rise of either cylinder pair alerts the CSTO circuitry, and the CSTO chip looks for the CSI input signal. The CSTO chip recognizes unique characteristics of the CSI input signal, then decides whether to send a camout high or camout low signal to the PCM. As the chart shows, when the 1-4 coil fires, as cylinder 1 is on compression, the event will generate negative, then positive CSI signal. This negative then positive CSI signal will cause the CSTO chip inside the E I module to send out a camout high signal. When the 1 4 coil fires, as cylinder 4 is on compression, the event will generate a positive, then negative CSI signal. This positive to negative CSI signal will cause the CSTO to send a camout low signal. The 2 3 cylinder pair works the same way. A variable reluctance crankshaft position, or CKP sensor, is mounted in the engine block near the crankshaft. The crankshaft has seven machined notches, six of which are evenly spaced. The seventh notch is used by the PCM as a sync pulse. 8-40

41 The 2 3 cylinder pair works the same way. A variable reluctance crankshaft position, or CKP sensor, is mounted in the engine block near the crankshaft. The crankshaft has seven machined notches, six of which are evenly spaced. The seventh notch is used by the PCM as a sync pulse. Figure 8-50, The engine always starts firing the 2 3 coil first during cranking. Charging of the 2 3 coil always begins near the second crank notch. Charging of the 1 4 coil always begins near the fifth crank notch. Once the ignition process has started with the 2 3 coil, the PCM will look for the sequence of camout signals from the E I module to determine engine phasing. The PCM needs to take into account engine operating conditions during which the in-cylinder pressures for the pairs can be nearly equal. Figure 8-51, During deceleration, the pressure of the compressing cylinder can be as low as, or lower than, that of the cylinder on its waste stroke. This condition would render the CSI signal information invalid. For this reason, the PCM will consider the CSI signal valid only during certain map ranges. 8-41

42 Distributor Ignition System Triggering The Distributor Ignition System, sometimes known as the High Voltage Switch, or HVS, system features a high energy ignition coil and ignition coil driver module. Each engine application of this enhanced ignition system has a unique distributor: Figure 8-52, Distributor Ignition System The 4.3 liter V 6 is non-adjustable. The 5.0, 5.7 and 7.4 liter V8s are all adjustable to eliminate the chance of crossfire only, not for timing adjustment. A magneto-resistive type crankshaft position sensor supplies trigger information for ignition timing. The crankshaft position sensor is located in the timing chain cover. The camshaft position sensor is located in the distributor base, and is used to sequence the fuel injectors and for onboard misfire diagnostics. The high voltage switch distributor appears similar to a typical distributor, but key operational features make it very different. Figure 8-53, High Voltage Switch Distributor 8-42

43 The HVS distributor does not provide engine position information for spark delivery. Therefore, rotating the HVS distributor does not change ignition base timing. The VCM contains the base timing information within its calibration. The ignition coil driver module is mounted with the high-energy coil. The vehicle control module, or VCM, controls the coil driver module. The coil driver module, in turn, controls current through the primary windings of the coil. Figure 8-54, Vehicle Control Module Base timing is not adjustable because the crank sensor determines it rather than the distributor. This makes it the main sensor for fuel and spark. As a result, the engine will not run without a crankshaft position sensor signal, because the ignition coil driver module doesn't have system trigger information. The HVS distributor ignition system uses crankshaft and camshaft position signals as inputs to the VCM. The VCM then uses the Ignition Control circuit to signal the coil driver module to control spark timing. The CKP sensor signal is used to determine engine position and speed. The CMP sensor signal identifies piston position. The CMP sensor is used to sequence the fuel injectors and detect misfire for O B D 2 diagnostics. The VCM uses the I C signal to control advance and retard based upon engine load, atmospheric pressure, RPM, and engine temperature. Because the distributor has no influence on base timing, turning it will not modify base timing in any way. However, the distributor on V 8 applications is adjusted to eliminate the chance of crossfire at an adjacent terminal. Distributor terminal crossfire can be evident by poor performance, as the control module will reduce the operating window for spark advance and retard. 8-43