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Engine Control System (Diagnostic Codes & Circuit Tests) (2ZR-FE): Overview Toyota Corolla XI

Testing & Diagnostics 14 illustrations ~2507 words

DESCRIPTION

The electronic throttle control system is composed of the throttle actuator, throttle position sensor, accelerator pedal position sensor, and ECM. The ECM operates the throttle actuator to regulate the throttle valve in response to driver inputs. The throttle position sensor detects the opening angle of the throttle valve, and provides the ECM with feedback so that the throttle valve can be appropriately controlled by the ECM.

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMILMemoryNote
P2119Throttle Actuator Control Throttle Body Range / PerformanceThe throttle valve opening angle continues to vary greatly from the target opening angle (1 trip detection logic).Electronic throttle control system Wire harness or connector ECMComes onDTC storedDTC for Mexico Models - Applies

MONITOR DESCRIPTION

The ECM determines the actual opening angle of the throttle valve from the throttle position sensor signal. The actual opening angle is compared to the target opening angle commanded by the ECM. If the difference between these two values is outside the standard range, the ECM interprets this as a malfunction in the electronic throttle control system. The ECM then illuminates the MIL and stores this DTC.

HINT

  1. This Electronic Throttle Control System (ETCS) does not use a throttle cable.
  2. These DTCs relate to the accelerator pedal position sensor.

The accelerator pedal position sensor is built into the accelerator pedal sensor assembly and has 2 sensor circuits: VPA (main) and VPA2 (sub). This sensor is a non-contact type sensor and uses Hall-effect elements in order to yield accurate signals even in extreme driving conditions, such as at high speeds as well as very low speeds. The voltage, which is applied to terminals VPA and VPA2 of the ECM, varies between 0.5 V and 4.75 V in proportion to the operating angle of the accelerator pedal (throttle valve). A signal from VPA indicates the actual accelerator pedal opening angle (throttle valve opening angle) and is used for engine control. A signal from VPA2 conveys the status of the VPA circuit and is used to check the accelerator pedal position sensor itself.

The ECM monitors the actual accelerator pedal opening angle (throttle valve opening angle) through the signals from VPA and VPA2, and controls the throttle actuator according to these signals.

Scheme 283

Scheme 283
DTC No.Detection ItemDTC Detection ConditionTrouble AreaMILMemoryNote
P2120Throttle / Pedal Position Sensor / Switch "D" CircuitVPA fluctuates rapidly beyond the upper and lower malfunction thresholds for 0.5 seconds or more (1 trip detection logic).Accelerator pedal sensor assembly ECMComes onDTC storedDTC for Mexico Models - Applies
P2122Throttle / Pedal Position Sensor / Switch "D" Circuit Low InputVPA is 0.4 V or less for 0.5 seconds or more when the accelerator pedal is depressed (1 trip detection logic).Accelerator pedal sensor assembly Open in VCPA circuit Open or ground short in VPA circuit ECMComes onDTC storedDTC for Mexico Models - Applies
P2123Throttle / Pedal Position Sensor / Switch "D" Circuit High InputVPA is 4.8 V or higher for 2.0 seconds or more (1 trip detection logic).Accelerator pedal sensor assembly Open in EPA circuit ECMComes onDTC storedDTC for Mexico Models - Applies
P2125Throttle / Pedal Position Sensor / Switch "E" CircuitVPA2 fluctuates rapidly beyond the upper and lower malfunction thresholds for 0.5 seconds or more (1 trip detection logic).Accelerator pedal sensor assembly ECMComes onDTC storedDTC for Mexico Models - Applies
P2127Throttle / Pedal Position Sensor / Switch "E" Circuit Low InputVPA2 is 1.2 V or less for 0.5 seconds or more when the accelerator pedal is depressed (1 trip detection logic).Accelerator pedal sensor assembly Open in VCP2 circuit Open or ground short in VPA2 circuit ECMComes onDTC storedDTC for Mexico Models - Applies
P2128Throttle / Pedal Position Sensor / Switch "E" Circuit High InputBoth of the following conditions continue for 2.0 seconds or more (1 trip detection logic): (a) VPA2 is 4.8 V or higher. (b) VPA is between 0.4 V and 3.45 V.Accelerator pedal sensor assembly Open in EPA2 circuit ECMComes onDTC storedDTC for Mexico Models - Applies
P2138Throttle / Pedal Position Sensor / Switch "D" / "E" Voltage CorrelationEither of the following conditions continues for 2.0 seconds or more (1 trip detection logic): (a) The difference between VPA and VPA2 is 0.02 V or less. (b) VPA is 0.4 V or less, and VPA2 is 1.2 V or less.Short between VPA and VPA2 circuits Accelerator pedal sensor assembly ECMComes onDTC storedDTC for Mexico Models - Applies

HINT

When any of these DTCs are output, check the accelerator pedal position sensor voltage using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Gas Throttle / Accel Sensor Out No. 1 and Accel Sensor Out No. 2.

Trouble AreaAccelerator Pedal Fully ReleasedAccelerator Pedal Fully Depressed
Accel Sensor Out No. 1Accel Sensor Out No. 2Accel Sensor Out No. 1Accel Sensor Out No. 2
Open in VCP circuit0 to 0.2 V0 to 0.2 V0 to 0.2 V0 to 0.2 V
Open or ground short in VPA circuit0 to 0.2 V1.2 to 2.0 V0 to 0.2 V3.4 to 4.75 V
Open or ground short in VPA2 circuit0.5 to 1.1 V0 to 0.2 V2.6 to 4.5 V0 to 0.2 V
Open in EPA circuit4.5 to 4.98 V4.5 to 4.98 V4.5 to 4.98 V4.5 to 4.98 V
Normal condition0.5 to 1.1 V1.2 to 2.0 V2.6 to 4.5 V3.4 to 4.75 V

HINT

Accelerator pedal positions are expressed as voltages.

When either output voltage of VPA or VPA2 deviates from the standard range, or the difference between the output voltages of the 2 sensor circuits is more than the threshold, the ECM determines that there is a malfunction in the accelerator pedal position sensor. The ECM then illuminates the MIL and stores a DTC.

Example

When the output voltage of VPA is 0.4 V or less for 0.5 seconds or more when the accelerator pedal is fully depressed, DTC P2122 is stored.

Refer to DTC P2120.

Refer to DESCRIPTION

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMILMemoryNote
P2121Throttle / Pedal Position Sensor / Switch "D" Circuit Range / PerformanceEither of the following conditions is met for 0.5 seconds (1 trip detection logic): Difference between VPA and VPA2 is less than 0.4 V, or higher than 1.2 V. (learned value of accelerator off position) Difference between VPA and VPA2 is greater than or equal to the specified value.Accelerator pedal sensor assembly ECMComes onDTC storedDTC for Mexico Models - Applies

The accelerator pedal position sensor is mounted on the accelerator pedal bracket. The accelerator pedal position sensor has 2 sensor elements and 2 signal outputs: VPA and VPA2. VPA is used to detect the actual accelerator pedal angle (used for engine control) and VPA2 is used to detect malfunctions in VPA. When the difference between the output voltages of VPA and VPA2 deviates from the standard, the ECM determines that the accelerator pedal position sensor is malfunctioning. The ECM illuminates the MIL and stores this DTC.

HINT

Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.

The air fuel ratio sensor generates a voltage* that corresponds to the actual air fuel ratio. This sensor voltage is used to provide the ECM with feedback so that it can control the air fuel ratio. The ECM determines the deviation from the stoichiometric air fuel ratio level, and regulates the fuel injection time. If the air fuel ratio sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.

The air fuel ratio sensor is a planar type and is integrated with a heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), current flows to the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are a narrow type. The heat generated by the heater is conducted to the solid electrolyte through alumina, and therefore the sensor activation is accelerated.

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a three-way catalytic converter is used. For the most efficient use of the three-way catalytic converter, the air fuel ratio must be precisely controlled so that it is always close to the stoichiometric level.

*: Value changes inside the ECM. Since the air fuel ratio sensor is a current output element, the current is converted into a voltage inside the ECM. Any measurements taken at the air fuel ratio sensor or ECM connectors will show a constant voltage.

Scheme 284

Scheme 284: DESCRIPTION
DTC No.Detection ItemDTC Detection ConditionTrouble AreaMILMemoryNote
P2195Oxygen (A/F) Sensor Signal Stuck Lean (Bank 1 Sensor 1)Either of following conditions 1 or 2 met: Conditions (a) and (b) continue for 5 seconds or more (2 trip detection logic): (a) Air fuel ratio sensor voltage is higher than 3.8 V. (b) Heated oxygen sensor voltage is 0.21 V or higher. While the fuel-cut operation is performed (during vehicle deceleration), the air fuel ratio sensor current is 2.2 mA or higher for 3 seconds (2 trip detection logic).Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) Exhaust gas leak Intake system Fuel pressure Fuel injector assembly ECMComes onDTC storedDTC for Mexico Models - Not apply
P2196Oxygen (A/F) Sensor Signal Stuck Rich (Bank 1 Sensor 1)Either of following conditions 1 or 2 met: Conditions (a) and (b) continue for 5 seconds or more (2 trip detection logic): (a) Air fuel ratio sensor voltage is less than 2.8 V. (b) Heated oxygen sensor voltage is less than 0.66 V. While the fuel-cut operation is performed (during vehicle deceleration), the air fuel ratio sensor current is less than 0.7 mA for 3 seconds (2 trip detection logic).Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) Exhaust gas leak Intake system Fuel pressure Fuel injector assembly ECMComes onDTC storedDTC for Mexico Models - Not apply

HINT

  1. When any of these DTCs is stored, check the air fuel ratio sensor voltage output by entering the following menus on the Techstream: Powertrain / Engine and ECT / Data List / Gas AF Control / AFS Voltage B1S1.
  2. Short-term fuel trim values can also be read using the Techstream.
  3. The ECM regulates the voltages at the A1A+ and A1A- terminals of the ECM to a constant level. Therefore, the air fuel ratio sensor output voltage cannot be confirmed without using the Techstream.
  4. If an air fuel ratio sensor malfunction is detected, the ECM will store a DTC.

Sensor Voltage Detection Monitor

Under air fuel ratio feedback control, If the air fuel ratio sensor output voltage is less than 2.8 V (very rich condition) for 5 seconds despite the heated oxygen sensor output voltage being less than 0.66 V, the ECM stores DTC P2196. Alternatively, if the air fuel ratio sensor output voltage is higher than 3.8 V (very lean condition) for 5 seconds despite the heated oxygen sensor output voltage being 0.21 V or higher, DTC P2195 is stored.

Sensor Current Detection Monitor

A rich air fuel mixture causes a low air fuel ratio sensor current, and a lean air fuel mixture causes a high air fuel ratio sensor current. Therefore, the sensor output becomes low during acceleration, and it becomes high during deceleration with the throttle valve fully closed. The ECM monitors the air fuel ratio sensor current during fuel-cut and detects any abnormal current values.

If the air fuel ratio sensor output is 2.2 mA or higher for more than 3 seconds of cumulative time, the ECM interprets this as a malfunction in the air fuel ratio sensor and stores DTC P2195 (stuck on high side). If the air fuel ratio sensor output is less than 0.7 mA for more than 3 seconds of cumulative time, the ECM stores DTC P2196 (stuck on low side).

Scheme 285

Scheme 285: MONITOR DESCRIPTION

Refer to DTC P0300.

Refer to DESCRIPTION

Refer to DTC P2195.

Refer to DESCRIPTION

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMILMemoryNote
P219ABank 1 Air-Fuel Ratio ImbalanceThe difference in air fuel ratios between the cylinders exceeds the threshold (2 trip detection logic).Fuel injector assembly Intake system Gas leaks from exhaust system Ignition system Compression pressure Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Not apply
P219CCylinder 1 Air-Fuel Ratio ImbalanceThe difference in air fuel ratios between the cylinders exceeds the threshold (2 trip detection logic).Fuel injector assembly Intake system Gas leaks from exhaust system Ignition system Compression pressure Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Not apply
P219DCylinder 2 Air-Fuel Ratio ImbalanceThe difference in air fuel ratios between the cylinders exceeds the threshold (2 trip detection logic).Fuel injector assembly Intake system Gas leaks from exhaust system Ignition system Compression pressure Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Not apply
P219ECylinder 3 Air-Fuel Ratio ImbalanceThe difference in air fuel ratios between the cylinders exceeds the threshold (2 trip detection logic).Fuel injector assembly Intake system Gas leaks from exhaust system Ignition system Compression pressure Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Not apply
P219FCylinder 4 Air-Fuel Ratio ImbalanceThe difference in air fuel ratios between the cylinders exceeds the threshold (2 trip detection logic).Fuel injector assembly Intake system Gas leaks from exhaust system Ignition system Compression pressure Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Not apply

Fuel System Air Fuel Ratio Cylinder Imbalance Monitor

The ECM uses the air fuel ratio sensor and crankshaft position sensor to monitor the difference in air fuel ratios between the cylinders caused by differences in injection volumes between the cylinders, leakage in the intake or exhaust system, etc.

When the air fuel ratios of the cylinders are lean or rich with respect to each other, the ECM determines that a problem is present and stores a DTC.

Air Fuel Ratio Sensor Monitoring Method: P219A is stored primarily when a rich side imbalance is detected.

When the system detects a difference in air fuel ratios between the cylinders due to fluctuation in the air fuel ratio sensor output over 1 engine cycle (2 crankshaft revolutions), the system determines that there is a problem.

Crankshaft Position Sensor Monitoring Method: P219C, P219D, P219E, and/or P219F are stored primarily when a lean side imbalance is detected.

The system monitors the engine speed variation and when the variation becomes large, the system determines that there is a difference in air fuel ratios between the cylinders, which it determines to be a problem.

Refer to DTC P2195.

Refer to DESCRIPTION

DTC No.Detection ItemDTC Detection ConditionTrouble AreaMILMemoryNote
P2237Oxygen (A/F) Sensor Pumping Current Circuit / Open (for A/F sensor) (Bank 1 Sensor 1)An open in the circuit between terminals A1A+ and A1A- of the air fuel ratio sensor while the engine is running (2 trip detection logic).Open in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Applies
P2238Oxygen Sensor Pumping Current Circuit Low (for A/F sensor) (Bank 1 Sensor 1)Case 1: Condition (a) or (b) continues for 5.0 seconds or more (2 trip detection logic):(a) Voltage at terminal A1A+ is 0.5 V or less(b) Voltage difference between terminals A1A+ and A1A- is 0.1 V or less Case 2: Air fuel ratio sensor admittance is less than 0.0054 1/ohms (2 trip detection logic).Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Applies
P2239Oxygen Sensor Pumping Current Circuit High (for A/F sensor) (Bank 1 Sensor 1)The A1A+ voltage is higher than 4.5 V (2 trip detection logic).Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Applies
P2252Oxygen Sensor Reference Ground Circuit Low (for A/F sensor) (Bank 1 Sensor 1)The A1A- voltage is 0.5 V or less (2 trip detection logic).Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Applies
P2253Oxygen Sensor Reference Ground Circuit High (for A/F sensor) (Bank 1 Sensor 1)The A1A- voltage is higher than 4.5 V (2 trip detection logic).Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECMComes onDTC storedDTC for Mexico Models - Applies

These DTCs are output when there is an open or short in the air fuel ratio sensor circuit, or if the air fuel ratio sensor output drops. To detect these problems, the voltage of the air fuel ratio sensor is monitored when turning the ignition switch to ON, and the admittance (admittance is an electrical term that indicates the ease of flow of current) is checked while driving. If the voltage of the air fuel ratio sensor is between 0.5 V and 4.5 V, it is considered normal. If the voltage is out of the specified range, or the admittance is less than the standard value, the ECM determines that there is a malfunction in the air fuel ratio sensor. If the same malfunction is detected in the next driving cycle, the ECM will illuminate the MIL and store a DTC.

The description can be found in EVAP (Evaporative Emission) System.

Refer to DESCRIPTION

5 hours* after the ignition switch is turned off, the leak detection pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure.

HINT

*: If the engine coolant temperature is not less than 35°C (95°F) 5 hours after the ignition switch is turned off, the monitor check starts 2 hours later. If it is still not less than 35°C (95°F) 7 hours after the ignition switch is turned off, the monitor check starts 2.5 hours later.

SequenceOperationDescriptionDuration
ECM activationActivated by soak timer, 5 hours (7 or 9.5 hours) after ignition switch is turned off.
AAtmospheric pressure measurementVent valve is turned off (vent) and EVAP system pressure is measured by ECM in order to register atmospheric pressure. If pressure in EVAP system is not between 70 kPa(abs) and 110 kPa(abs) [525 mmHg(abs) and 825 mmHg(abs)], ECM cancels EVAP system monitor.60 seconds
BFirst reference pressure measurementIn order to determine reference pressure, leak detection pump creates negative pressure (vacuum) through reference orifice and then ECM checks if leak detection pump and vent valve operate normally.360 seconds
CEVAP system pressure measurementVent valve is turned on (closed) to shut EVAP system. Negative pressure (vacuum) is created in EVAP system, and then EVAP system pressure is measured. Write down measured value as they will be used in leak check. If EVAP pressure does not stabilize within 15 minutes, ECM cancels EVAP system monitor.15 minutes*
DPurge VSV monitorPurge VSV is opened and then EVAP system pressure is measured by ECM. Large increase indicates normal.10 seconds
ESecond reference pressure measurementAfter second reference pressure measurement, leak check is performed by comparing first and second reference pressure measurements. If stabilized system pressure is higher than second reference pressure, ECM determines that there is a leak in EVAP system.60 seconds
Final checkAtmospheric pressure is measured and then monitoring result is recorded by ECM.

*: If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.

Scheme 286

Scheme 286
*1Purge VSV: Off (Closed)*2Purge VSV: On (Open)
*3Vent Valve: Off (Vent)*4Vent Valve: On (Closed)
*5Leak Detection Pump: Off*6Leak Detection Pump: On
*7Reference Orifice (0.02 inch)*8Canister Pressure Sensor
*9Canister*10Fuel Tank
*11Canister Pump Module*12Canister Filter
*aOperation A: Atmospheric Pressure Measurement*bOperation B, E: Reference Pressure Measurement
*cOperation C: EVAP System Pressure Measurement*dOperation D: Purge VSV Monitor
*eAtmospheric Pressure*fNegative Pressure

P2420: Vent valve stuck open (vent)

In operation C, the vent valve turns on (closed) and the EVAP system pressure is then measured by the ECM using the canister pressure sensor to conduct an EVAP leak check. If the pressure does not increase when the vent valve is open, the ECM interprets this as the vent valve being stuck open. In this case the ECM will illuminate the MIL and store this DTC.

Scheme 287

Scheme 287

The soak timer operates after the ignition switch is turned off. When a certain amount of time has elapsed after turning the ignition switch off, the soak timer activates the ECM to perform malfunction checks which can only be performed after the engine is stopped. The soak timer is built into the ECM.

Scheme 288

Scheme 288: DESCRIPTION

If the soak timer activates the ECM even though only a short amount of time has elapsed since the ignition switch was turned off, or if the soak timer does not activate the ECM even though a considerable amount of time has elapsed since the ignition switch was turned off, the ECM determines that the soak timer is malfunctioning, illuminates the MIL and stores this DTC the next time the ignition switch is turned to ON.

When the ignition switch is turned to ON, the battery voltage is applied to IGSW of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil, closing the contacts of the EFI-MAIN relay and supplying power to terminals +B and +B2 of the ECM.

Scheme 289

Scheme 289: WIRING DIAGRAM

The ECM constantly generates a 5 V power source voltage from the battery voltage supplied to the +B (BATT) terminal to operate the microprocessor. The ECM also provides this power source voltage to the sensors through the VC output circuit.

Scheme 290

Scheme 290: DESCRIPTION

When the VC circuit is short-circuited, the microprocessor in the ECM and the sensors that are supplied with power through the VC circuit are inactivated because power is not supplied from the VC circuit. Under this condition, the system does not start up and the MIL does not illuminate even if the system malfunctions.

HINT

Under normal conditions, the MIL is illuminated when the ignition switch is turned to ON. The MIL goes off when the engine is started.

Scheme 291

Scheme 291: WIRING DIAGRAM

Scheme 292

Scheme 292

When the engine is cranked, the starter (ST NO. 1) relay drive signal output from the ignition switch assembly*1 or certification ECU (smart key ECU assembly)*2 is input into the STA terminal of the ECM, and the NE signal generated by the crankshaft position sensor is also input into the NE+ terminal. The ECM interprets that the engine is cranked, and turns transistor Tr1 in the ECM internal circuit on. Current flows to the C/OPN (Circuit Opening) relay by turning Tr1 on. Then, the fuel pump operates.

While the NE signal is input into the ECM with the engine running, the ECM turns Tr1 on continuously.

*1: w/o smart key system.

*2: w/ smart key system.

Scheme 293

Scheme 293: WIRING DIAGRAM

The fuel injectors are located on the intake manifold. They inject fuel into the cylinders based on the signals from the ECM.

Scheme 294

Scheme 294: WIRING DIAGRAM

While the engine is being cranked, current flows from terminal ST2 of the ignition switch assembly*1 or terminal STAR of the certification ECU (smart key ECU assembly)*2 to the park/neutral position switch assembly*3 or clutch start switch assembly*4 and to terminal STA of the ECM (STA signal).

*1: w/o smart key system.

*2: w/ smart key system.

*3: for CVT and A/T models.

*4: for M/T models.

When the vehicle is being driven, depressing the accelerator pedal sensor assembly and brake pedal will activate the brake override system to restrict driving torque. The conditions for activating the brake override system as well as the items that are controlled are explained below.

Scheme 295

Scheme 295: DESCRIPTION

Activation Conditions

  1. Vehicle is running at or above the specified speed.
  2. When the accelerator pedal and brake pedal are depressed.

Note. The vehicle may not enter the brake override system control due to the relation of the accelerator pedal angle and the vehicle's speed.

Items Controlled

  1. Driving torque is restricted.

HINT

When this control is activated, the accelerator opening value is forcibly reduced to a fixed value. Therefore, the Accelerator Position value in the Data List is fixed regardless of the actual accelerator opening value (Accel Sens. No. 1 Volt %).

Deactivation Conditions

  1. When the brake pedal or the accelerator pedal returns to some degree.

The MIL (Malfunction Indicator Lamp) is used to indicate vehicle malfunctions detected by the ECM. When the ignition switch is turned to ON, power is supplied to the MIL circuit, and the ECM provides the circuit ground which illuminates the MIL.

The MIL operation can be checked visually: When the ignition switch is turned to ON, the MIL should be illuminated and should turn off after engine is started. If the MIL remains illuminated or is not illuminated, conduct the following troubleshooting procedure using the Techstream.

Scheme 296

Scheme 296: WIRING DIAGRAM