14. Engine Control System

Transcription

1 48 4. Engine Control System General The engine control system of the 2GR-FE engine has the following features. The Engine ECU that controls this system is made by DENSO. System EFI (Electric Fuel Injection) [See page 63] ESA (Electronic Spark Advance) ETCS-i (Electronic Throttle Control System-intelligent) [See page 64] Dual VVT-i (Dual Variable Valve Timing-intelligent) [See page 66] ACIS (Acoustic Control Induction System) [See page 72] Air Intake Control System [See page 74] Fuel Pump Control [See page 75] Air Conditioner Cut-off Control Cooling Fan Control [See page 76] Air Fuel Ratio and Oxygen Heater Control Evaporative Emission Control Active Control Engine Mount [See page 46] Engine Immobilizer Diagnosis [See page 78] Fail-Safe [See page 78] Outline An L-type EFI system directly detects the intake air volume with a hot-wire type air flow meter. Ignition timing is determined by the Engine ECU based on signals from various sensors. The Engine ECU corrects ignition timing in response to engine knocking. This system selects the optimal ignition timing in accordance with the signals received from the sensors and sends (IGT) ignition signals to the igniters. Optimally controls the opening angle of the throttle valve in accordance with the accelerator pedal input and the engine and vehicle conditions. Controls the intake and exhaust camshafts to an optimal valve timing in accordance with the engine operating conditions. The intake air passages are switched based on engine speed and throttle valve opening angle to provide high performance in all engine speed ranges. The Engine ECU selects between using one, or using both intake air ducts, in order to choose the option that provides the most appropriate balance of noise reduction and airflow for the engine operating conditions. Fuel pump operation is controlled by signals from the Engine ECU. The fuel pump is stopped when an SRS airbag is deployed in a frontal, side, or rear side collision. By turning the air conditioner compressor ON or OFF in accordance with the engine conditions, drivability is maintained. The Cooling Fan ECU steplessly controls the speed of the fans in accordance with the engine coolant temperature, vehicle speed, engine speed, and air conditioning operating conditions. As a result, the cooling performance is improved. Maintains the temperature of the air fuel ratio sensors or oxygen sensors at an appropriate level to increase the ability of the sensor to accurately detect oxygen concentration. The Engine ECU controls the purge flow of evaporative emission (HC) in the charcoal canister in accordance with engine conditions. The damping characteristics of the front engine mount are varied to reduce idle vibration. Prohibits fuel delivery and ignition if an attempt is made to start the engine with an invalid ignition key. When the Engine ECU detects a malfunction, the Engine ECU records the malfunction and information that relates to the fault. When the Engine ECU detects a malfunction, the Engine ECU stops or controls the engine according to the data already stored in the memory.

2 49 Construction The configuration of the engine control system is as shown in the following chart. SENSORS AIR FLOW METER INTAKE AIR TEMP. SENSOR CRANKSHAFT POSITION SENSOR VG THA NE #0 #20 #30 #40 #50 #60 ACTUATORS EFI No. INJECTOR No.2 INJECTOR No.3 INJECTOR No.4 INJECTOR No.5 INJECTOR No.6 INJECTOR WATER TEMP. SENSOR THW IGT ~ IGT6 ESA ACCELERATOR PEDAL POSITION SENSOR VPA VPA2 IGF IGNITION COILS (with IGNITER) SPARK PLUGS THROTTLE POSITION SENSOR VTA VTA2 Engine ECU M ETCS-i THROTTLE CONTROL MOTOR KNOCK SENSORS KNK KNK2 VVT-i (INTAKE SIDE) INTAKE VVT SENSORS VV VV2 OC CAMSHAFT TIMING OIL CONTROL VALVE RH EXHAUST VVT SENSORS EV EV2 OC2 CAMSHAFT TIMING OIL CONTROL VALVE LH STOP LIGHT SWITCH STP VVT-i (EXHAUST SIDE) COMBINATION METER SPD OE CAMSHAFT TIMING OIL CONTROL VALVE RH Vehicle Speed Signal GATEWAY ECU BEAN AIRBAG SENSOR ASSEMBLY CAN OE2 ACIS CAMSHAFT TIMING OIL CONTROL VALVE LH ACIS ACIS ACTUATOR 0270EG07C (Continued)

3 50 IGNITION SWITCH STA IGSW AICV AIR INTAKE CONTROL SYSTEM VSV NEUTRAL START SWITCH P, R, N, D FUEL PUMP CONTROL SHIFT LOCK ECU* (TRANSMISSION CONTROL SWITCH) 4, L FC FPR CIRCUIT OPENING RELAY FUEL PUMP RELAY S COOLING FAN CONTROL TRANSMISSION CONTROL SWITCH* 2 SFTU SFTD RFC COOLING FAN ECU FAN MOTOR No., No.2 AIR FUEL RATIO SENSOR (Bank, ) (Bank 2, ) HEATED OXYGEN SENSOR (Bank, 2) (Bank 2, 2) AA+ A2A+ OXB OX2B Engine ECU HAA HA2A HAB HA2B A/F SENSOR & OXYGEN SENSOR HEATER CONTROL A/F SENSOR HEATER (Bank, ) (Bank 2, ) OXYGEN SENSOR HEATER (Bank, 2) (Bank 2, 2) POWER STEERING OIL PRESSURE SWITCH TRANSPONDER KEY ECU PSW IMI IMO PRG EVAPORATIVE EMISSION CONTROL EVAP VALVE DLC3 TC CAN ACM ACTIVE CONTROL ENGINE MOUNT VSV BATTERY BATT EFI MAIN RELAY MREL +B W COMBINATION METER CHECK ENGINE WARNING LIGHT * : Without Multi-Mode Automatic Transmission * 2 : With Multi-Mode Automatic Transmission 0280EG03C

4 Engine Control System Diagram 5 Combination Meter Vehicle Speed Signal Check Engine Warning Light Fuel Pump Resistor Ignition Switch Circuit Opening Relay EFI Main Relay Power Steering Oil Pressure Switch Neutral Start Switch Electronic Controlled Transmission Solenoid Valve Fuel Pump Relay Battery Gateway ECU CAN J/C CAN DLC3 BEAN Airbag Assembly Cooling Fan ECU Stop Light Switch Accelerator Pedal Position Fuel Pump Engine ECU Throttle Control Motor Intake Air Temp. EVAP Valve VSV (For Active Control Engine Mount) ACIS Actuator Charcoal Canister VSV (For Air Intake Control) Air Air Flow Meter Throttle Position Exhaust VVT RH Intake Camshaft Timing Oil Control Valve RH Intake VVT RH Ignition Coil With Igniter Injector Intake Camshaft Timing Oil Control Valve LH Injector Intake VVT LH Exhaust Camshaft Timing Oil Control Valve RH Exhaust VVT LH Air Fuel Ratio (Bank, ) TWC Heated Oxygen (Bank, 2) Water Temp. TWC Knock Crankshaft Position Exhaust Camshaft Timing Oil Control Valve LH TWC Heated Oxygen (Bank 2, 2) Air Fuel Ratio (Bank 2, ) 0280EG04C

5 52 Layout of Main Components Heated Oxygen (Bank, 2) VSV (For Active Control Engine Mount) Heated Oxygen (Bank 2, 2) Fuel Pump Cooling Fan ECU Air Cleaner Cap Vacuum Tank Air Flow Meter Intake Air Temp. Circuit Opening Relay Fuel Pump Relay A/F Relay 0280EG05Z Starter Relay IG2 Relay Engine Room R/B EFI Main Relay Combination Meter Check Engine Warning Light EVAP Valve Actuator (For Air Intake Control) VSV (For Air Intake Control) Accelerator Pedal Position Stop Light Switch DLC3 Engine ECU 0280EG06C

6 53 Intake Camshaft Timing Oil Control Valve LH (OC2) Intake VVT LH (VV2) Ignition Coil with Igniter Injector Water Temp. Intake Camshaft Timing Oil Control Valve RH (OC) Exhaust VVT RH (EV) Intake VVT RH (VV) Exhaust Camshaft Timing Oil Control Valve LH (OE2) Crankshaft Position Air Fuel Ratio (Bank 2, ) Exhaust VVT LH (EV2) Air Fuel Ratio (Bank, ) Exhaust Camshaft Timing Oil Control Valve RH (OE) 0270EG32C ACIS Actuator Throttle Position Knock (KNK) Knock 2 (KNK2) 285EG50

7 54 Main Components of Engine Control System ) General The main components of the engine control system are as follows: Components Outline Quantity Engine ECU 32-bit CPU Air Flow Meter Hot-wire Type Crankshaft Position (Rotor Teeth) Pick-up Coil Type (36-2) Intake VVT (Rotor Teeth) MRE (Magnetic Resistance Element) Type (3) 2 ( each bank) Exhaust VVT (Rotor Teeth) MRE (Magnetic Resistance Element) Type (3) 2 ( each bank) Accelerator Pedal Position Linear (Non-Contact) Type Throttle Position Linear (Non-Contact) Type Knock Built-in Piezoelectric Type (Non-resonant Type/Flat Type) 2 ( each bank) Air Fuel Ratio (Bank, ) Heated Type (Planar Type) 2 (Bank 2, ) ( each bank) Heated Oxygen (Bank, 2) Heated Type (Cup Type) 2 (Bank 2, 2) ( each bank) Injector 2-hole Type 6

8 55 2) Air Flow Meter D The air flow meter, which is a slot-in type, allows a portion of the intake air to flow through the detection area. By directly measuring the mass and the flow rate of the intake air, the detection precision is improved and the intake air resistance is reduced. D This air flow meter has a built-in intake air temperature sensor. A Platinum Hot-Wire Element Air Flow Temperature Sensing Element Intake Air Temp. A A - A Cross Section 0270EG8C 3) Crankshaft Position The timing rotor of the crankshaft consists of 34 teeth with 2 teeth missing. The crankshaft position sensor outputs the crankshaft rotation signals every 0, and the change of the signal due to the missing teeth is used to determine top-dead-center. NE Signal Plate (720_ CA) Engine Front 0_ CA Timing Rotor Crankshaft Position 2 Teeth Missing 285EG79 279EG50

9 56 4) Intake and Exhaust VVT s a. General MRE (Magnetic Resistance Element) type intake and exhaust VVT sensors are used. To detect each intake camshaft position, a timing rotor that is secured to the camshaft in front of the VVT controller is used to generate 6 (3 Hi Output, 3 Lo Output) pulses for every 2 revolutions of the crankshaft. The timing rotor for each exhaust camshaft is part of the respective camshaft. Intake VVT RH Exhaust VVT RH Timing Rotor Intake VVT (Right Bank) 285EG82 Timing Rotor Exhaust VVT (Right Bank) 285EG83 " Output Waveforms A VVT Signal Plate (720_ CA) 60_ CA 80_ CA 20_ CA VVT 80_ CA 60_ CA 20_ CA 0V Crankshaft Position 360_ CA 360_ CA 0V 0_ CA 285EG84

10 57 b. MRE Type VVT D An MRE type VVT sensor consists of an MRE, a magnet and a sensor. The direction of the magnetic field changes due to the profile (protruding and non-protruding portions) of the timing rotor, which passes by the sensor. As a result, the resistance of the MRE changes, and the output voltage to the Engine ECU changes to Hi or Lo. The Engine ECU detects the camshaft position based on this output voltage. D The differences between an MRE type VVT sensor and a pickup coil type VVT sensor used on a conventional model are as follows. Item Signal Output Camshaft Position Detection Type MRE Pick-up Coil Constant digital output starts from low Analog output changes with the engine engine speeds. speed. Camshaft position detection is made by comparing the NE signal with the Hi/Lo output switch timing of the VVT sensor which is due to the protruding/non-protruding portions of the timing rotor. Camshaft detection can also be made based on the number of the NE signals input during a Hi/Lo output. Detection is made by comparing the NE signals with the change of waveform that is output when the protruding portion of the timing rotor passes. " Wiring Diagram A Intake VVT RH VC VV+ VV- Engine ECU Timing Rotor Intake VVT RH 27EG60 " MRE Type and Pick-up Coil Type Output Waveform Image Comparison A No Detecting Engine Speed Engine Speed Analog Output Output Digital Output Output MRE Type Pick-up Coil Type 232CH4

11 58 5) Accelerator Pedal Position The non-contact type accelerator pedal position sensor uses a Hall IC, which is mounted on the accelerator pedal arm. D The magnetic yoke that is mounted at the base of the accelerator pedal arm moves around the Hall IC in accordance with the amount of effort that is applied to the accelerator pedal. The Hall IC converts the changes in the magnetic flux that occur into electrical signals, and outputs them in the form of accelerator pedal position signals to the Engine ECU. D The Hall IC contains two circuits, one for the main signal, and one for the sub signal. It converts the accelerator pedal position (angle) into electric signals that have differing characteristics and outputs them to the Engine ECU. Hall IC Magnetic Yoke Accelerator Pedal Arm 0270EG9C Accelerator Pedal Position Magnet VPA EPA 5 V Hall IC Hall IC VCPA VPA2 EPA2 VCP2 Engine ECU Output Voltage 0 VPA2 VPA Magnet 228TU24 Fully Closed Accelerator Pedal Position (Angle) Fully Open 040EG26C Service Tip The inspection method differs from a conventional accelerator pedal position sensor because this sensor uses a Hall IC. For details, refer to the LEXUS RX350 Repair Manual Supplement (Pub. No. RM0280E).

12 59 6) Throttle Position This non-contact type throttle position sensor uses a Hall IC, which is mounted on the throttle body. D The Hall IC is surrounded by a magnetic yoke. The Hall IC converts the changes that occur in the magnetic flux into electrical signals, and outputs them in the form of throttle valve position signals to the Engine ECU. D The Hall IC contains circuits for the main and sub signals. It converts the throttle valve opening angle into electric signals that have differing characteristics, and outputs them to the Engine ECU. Throttle Body Throttle Position Portion A View from A Magnet Hall IC (for Throttle Position ) Magnet Cross Section 238EG59 Throttle Position Magnet Hall IC Hall IC VTA E VC VTA2 Engine ECU Output Voltage V VTA2 VTA Magnet 230LX2 Throttle Valve Fully Closed Throttle Valve Opening Angle Throttle Valve Fully Open Service Tip The inspection method differs from a conventional throttle position sensor because this sensor uses a Hall IC. For details, refer to the LEXUS RX350 Repair Manual Supplement (Pub. No. RM0280E). 238EG79

13 60 7) Knock (Flat Type) a. General In a conventional type knock sensor (resonant type), a vibration plate is built into the sensor. This plate has the same resonance point as the knocking* frequency of the engine block. This sensor can only detect vibration in this frequency band. The other type of knock sensor, a flat type knock sensor (non-resonant type) has the ability to detect vibration in a wider frequency band (from about 6 khz to 5 khz). It has the following features: D The engine knocking frequency will vary slightly depending on the engine speed. The flat type knock sensor can detect vibration even when the engine knocking frequency changes. Due to the use of the flat type knock sensor, the vibration detection ability is increased compared to a conventional type knock sensor, and more precise ignition timing control is possible. *: The term Knock or Knocking is used in this case to describe either preignition or detonation of the air fuel mixture in the combustion chamber. This preignition or detonation refers to the air fuel mixture being ignited earlier than is advantageous. This use of Knock or Knocking is not primarily used to refer to a loud mechanical noise that may be produced by an engine. : Resonance Characteristic of Conventional Type : Resonance Characteristic of Flat Type (V) Voltage A A: Detection Band of Conventional Type B: Detection Band of Flat Type B Frequency (Hz) Characteristic of Knock 24EG04 b. Construction D A flat type knock sensor is installed to an engine by placing it over the stud bolt installed on the cylinder block. For this reason, a hole for the stud bolt exists in the center of the sensor. D In the sensor, a steel weight is located in the upper portion. An insulator is located between the weight and a piezoelectric element. D An open/short circuit detection resistor is integrated in the sensor. Steel Weight Open Circuit Detection Resistor Piezoelectric Element Insulator Piezoelectric Element Vibration Plate Flat Type Knock (Non-Resonant Type) 24CE0 Conventional Type Knock (Resonant Type) 24CE02

14 6 c. Operation Vibrations caused by knocking are transmitted to the steel weight. The inertia of this weight applies pressure to the piezoelectric element. This action generates electromotive force. Steel Weight Inertia Piezoelectric Element 24CE08 d. Open/Short Circuit Detection Resistor When the ignition is ON, the open/short circuit detection resistor in the knock sensor and the resistor in the Engine ECU keep the voltage at terminal KNK constant. An IC (Integrated Circuit) in the Engine ECU constantly monitors the voltage of terminal KNK. If the open/short circuit occurs between the knock sensor and the Engine ECU, the voltage of terminal KNK will change and the Engine ECU will detect the open/short circuit and store a DTC (Diagnostic Trouble Code). Piezoelectric Element Flat Type Knock KNK 5V 200 k Engine ECU 200 k EKNK IC Open/Short Circuit Detection Resistor 24CE06 Service Tip These knock sensors are mounted in the specific directions and angles as illustrated. To prevent the right and left bank connectors from being interchanged, make sure to install each sensor in its prescribed direction. Knock RH Engine Front Knock LH 285EG55

15 62 8) Air Fuel Ratio and Heated Oxygen a. General D A planar type air-fuel ratio sensor and a cup type heated oxygen sensor are used. D The basic construction of the oxygen sensor and the air-fuel ratio sensor is the same. However, they are divided into the cup type and the planar type, according to the different types of heater construction used. D The planar type air-fuel ratio sensor uses alumina, which excels in heat conductivity and electrical insulation, to integrate a sensor element with a heater, thus improving the warm-up performance of the sensor. D The cup type heated oxygen sensor contains a sensor element that surrounds a heater. Dilation Layer Alumina Atmosphere Platinum Electrode Heater Atmosphere Alumina Heater Platinum Electrode Element (Zirconia) Air Fuel Ratio (Planar Type) b. Characteristics Element (Zirconia) Heated Oxygen (Cup Type) 279EG8 As illustrated below, the conventional heated oxygen sensor is characterized by a sudden change in its output voltage at the threshold of the stoichiometric air-fuel ratio (4.7:). In contrast, the air-fuel ratio sensor data is approximately proportionate to the existing air-fuel ratio. The air-fuel ratio sensor converts the oxygen density to current and sends it to the Engine ECU. As a result, the detection precision of the air-fuel ratio has been improved. The air-fuel ratio sensor data can only be read using an intelligent tester II. : Air-Fuel Ratio : Heated Oxygen (V) 4.2 (V) Air-Fuel Ratio Data Displayed on Hand-held Tester Heated Oxygen Output (Rich) (Lean) Air Fuel Ratio D3N *: This calculation value is used internally in Engine ECU and is not an Engine ECU terminal voltage.