Engine Control (Sfi) System (Diagnostic Codes (P2102-U0293) & Circuit Tests) (Except Phv): Overview Toyota Prius III

DESCRIPTION

The throttle actuator is operated by the ECM and opens and closes the throttle valve using gears.

The opening angle of the throttle valve is detected by the throttle position sensor, which is mounted on the throttle body assembly. The throttle position sensor provides feedback to the ECM. This feedback allows the ECM to appropriately control the throttle actuator and monitor the throttle opening angle as the ECM responds to driver inputs.

HINT

This electronic throttle control system does not use a throttle cable.

MONITOR DESCRIPTION

The ECM monitors the electrical current through the electronic actuator, and detects malfunctions and open circuits in the throttle actuator based on this value. If the current is outside the standard range, the ECM determines that there is a malfunction in the throttle actuator. In addition, if the throttle valve does not function properly (for example, stuck on), the ECM determines that there is a malfunction. The ECM then illuminates the MIL and stores a DTC.

Example

1. When the electrical current is below 0.5 A and the throttle actuator duty ratio exceeds 80%, the ECM interprets this as the current being outside the standard range, illuminates the MIL and stores a DTC.
2. If the malfunction is not repaired successfully, a DTC is stored when the engine is quickly revved to a high engine speed several times after the engine has idled for 5 seconds after engine start.

The throttle actuator is operated by the ECM, and opens and closes the throttle valve using gears. The opening angle of the throttle valve is detected by the throttle position sensor, which is mounted on the throttle body assembly. The throttle position sensor provides feedback to the ECM. This feedback allows the ECM to appropriately control the throttle actuator and monitor the throttle opening angle as the ECM responds to driver inputs.

HINT

This electronic throttle control system does not use a throttle cable.

The ECM determines that there is a malfunction in the electronic throttle control system when the throttle valve remains at the fixed angle despite a high drive current from the ECM. The ECM illuminates the MIL and stores a DTC.

If the malfunction is not repaired successfully, a DTC is stored when the accelerator pedal is fully depressed and released quickly (to fully open and close the throttle valve) after the engine is next started.

The electronic throttle control system has a dedicated power supply circuit. The voltage (+BM) is monitored and when it is low (below 4 V), the ECM determines that there is a malfunction in the electronic throttle control system and cuts off the current to the throttle actuator.

When the voltage becomes unstable, the electronic throttle control system itself becomes unstable. For this reason, when the voltage is low, the current to the throttle actuator is cut. If repairs are made and the system returns to normal, turn the power switch off. The ECM then allows the current to flow to the throttle actuator so that it can be restarted.

HINT

This electronic throttle control system does not use a throttle cable.

Scheme 138

The ECM monitors the battery supply voltage applied to the throttle actuator.

When the power supply voltage (+BM) drops below 4 V for 0.8 seconds or more, the ECM interprets this as an open in the power supply circuit (+BM). The ECM illuminates the MIL and stores the DTC.

If the malfunction is not repaired successfully, the DTC is stored 5 seconds after the engine is next started.

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.

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 2 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 the DTC.

If the malfunction is not repaired successfully, the DTC is stored when the accelerator pedal is quickly released (to close the throttle valve) after the engine speed reaches 5000 rpm by depressing the accelerator pedal (fully open the throttle valve).

HINT

1. Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.
2. Sensor 1 refers to the sensor mounted in front of the three-way catalytic converter and located near the engine assembly.

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 the planar type and is integrated with the 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), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are the narrow type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, therefore the sensor activation is accelerated.

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbons (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 139

HINT

1. When any of these DTCs are set, check the air fuel ratio sensor voltage output by entering the following menus on the Techstream: Powertrain / Engine and ECT / Data List / All Data / 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 voltage output cannot be confirmed without using the Techstream.
4. If an air fuel ratio sensor malfunction is detected, the ECM sets a DTC.

Sensor Voltage Detection Monitor

Under the air fuel ratio feedback control, if the air fuel ratio sensor voltage output indicates rich or lean for a certain period of time, the ECM determines that there is a malfunction in the air fuel ratio sensor. The ECM illuminates the MIL and stores a DTC.

Example

If the air fuel ratio sensor voltage output is below 2.8 V (very rich condition) and heated oxygen sensor output voltage falls from 0.59 V or more to less than 0.21 V for 5 seconds, the ECM stores DTC P2196. Alternatively, if the air fuel ratio sensor voltage output is higher than 3.8 V (very lean condition) and heated oxygen sensor output voltage rises from less than 0.21 V to 0.59 V or more for 5 seconds, 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 3.6 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 below 1.57 mA for more than 3 seconds of cumulative time, the ECM stores DTC P2196 (stuck on low side).

Scheme 140

HINT

1. Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.
2. Sensor 1 refers to the sensor mounted in front of the three-way catalytic converter and located near the engine assembly.

The air fuel ratio sensor, which is located between the exhaust manifold and catalyst, consists of alloyed metal elements and a heater.

Depending on the engine operating conditions, the heater heats the sensor elements to activate them. Battery voltage is applied to the heater and the sensor ground is controlled by the ECM using a duty ratio.

The sensor elements convert the oxygen concentration in the exhaust gas into voltage values to output. Based on the voltage, the ECM determines the air fuel ratio and regulates the fuel injection volume depending on the air fuel ratio and engine operating conditions. The voltage changes between 0.6 V and 4.5 V while the engine is running. If the air fuel ratio is lean, which means the oxygen concentration in the exhaust gas is high, the voltage is high. If the air fuel ratio is rich, which means the oxygen concentration in the exhaust gas is low, the voltage is low.

Scheme 141

These DTCs are output when there is an open or short in the air fuel ratio sensor circuit, or if air fuel ratio sensor output drops. To detect these problems, the voltage of the air fuel ratio sensor is monitored when turning the power switch on (IG), 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 will determine that there is a malfunction in the air fuel ratio sensor. If the same malfunction is detected in next driving cycle, the MIL will be illuminated and a DTC will be stored.

The circuit description can be found in the EVAP (Evaporative Emission) System. Refer to DESCRIPTION.

5 hours*1 after the power 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

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

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

Scheme 142

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. The ECM illuminates the MIL and sets the DTC.

Scheme 143

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

Scheme 144

If the soak timer activates the ECM even though only a short amount of time has elapsed since the power 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 power switch was turned off, the ECM determines that the soak timer is malfunctioning, illuminates the MIL and stores a DTC the next time the power switch is turned on (IG).

While the engine is running, the ECM monitors the synchronization of the soak timer and the CPU clock. If these two are not synchronized, the ECM interprets this as a malfunction, illuminates the MIL and sets the DTC (2 trip detection logic).

The ECM controls the engine water pump assembly by calculating the necessary amount of coolant flow based on engine coolant temperature, engine speed and vehicle speed information. The speed of the engine water pump assembly is controlled steplessly using duty cycle signal sent from the ECM. This optimal control enhances warm-up performance and reduces cooling losses, thus reducing the specific fuel consumption of the engine.

The ECM calculates the speed of the engine water pump assembly using a duty cycle signal sent from the engine water pump assembly. When the speed of the engine water pump assembly becomes less than 900 rpm while it is operating, the ECM detects the malfunction and stores DTC P261B.

The engine water pump assembly operates steplessly based on a duty cycle signal sent from the ECM. The ECM monitors the current of the engine water pump assembly. If actual drive duty cycle ratio does not correspond to the target drive duty cycle , the ECM detects the malfunction and stores DTC P261C and P261D.

HINT

1. Refer to DTC P2195. Refer to «DESCRIPTION»(ref-393184-S09399602042011040700000).
2. Sensor 1 refers to the sensor mounted in front of the three-way catalytic converter and located near the engine assembly.

After the engine is warmed up, the ECM performs air fuel ratio feedback control to maintain the air fuel ratio at the stoichiometric level. In addition, active A/F control is performed for approximately 15 to 20 seconds after preconditions are met in order to measure the air fuel ratio sensor response rate. During active A/F control, the ECM forcibly increases and decreases the injection volume a certain amount, based on the stoichiometric air fuel ratio learned during normal air fuel ratio control, and measures the air fuel ratio sensor response rate. The ECM receives a signal from the air fuel ratio sensor while performing active A/F control and uses it to calculate the air fuel ratio sensor response rate deterioration level.

If the value for air fuel ratio sensor response rate deterioration level is beyond the threshold, the ECM interprets this as a malfunction and sets the DTC.

Scheme 145

From the power management control ECU, the ECM receives data such as power output required for the engine (required output), estimated torque produced by the engine (estimated torque), engine speed of control target (target speed), and whether the engine is in start mode or not. Then, based on the required output and target speed, the ECM calculates a target torque that is to be produced by the engine and compares it with the estimated torque. If the estimated torque is very low compared with the target torque, or the engine start mode continues for the specific duration calculated by the coolant temperature, an abnormal condition is detected.

The ECM and power management control ECU are connected by a communication line called CAN. The ECM sends engine speed data and other data to the power management control ECU while the power management control ECU sends the information such as a requirement for the engine power to the ECM using the CAN communication line. When the communication between the ECM and power management control ECU is normal and the following items become a specified condition, the ECM illuminates the MIL and sets a DTC.

1. Engine speed
2. Target torque
3. Ratio of target torque against estimated torque
4. Fuel level

The Controller Area Network (CAN) is a serial data communication system for real-time application. It is a multiplex communication system designed for on-vehicle use that provides a superior communication speed of 500 kbps and a capability to detect malfunctions. Through the combination of the CANH and CANL bus lines, the CAN is able to maintain communication based on differential voltage.

When the power switch is turned on (IG), 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 integration relay (EFI MAIN relay) and supplying power to either terminal +B and +B2 of the ECM.

Scheme 146

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

Scheme 147

When the VC circuit is shorted, the microprocessor in the ECM and sensors that are supplied power through the VC circuit are inactivated because the 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 for several seconds when the power switch is first turned on (IG). The MIL goes off when the engine is started.

Scheme 148

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Scheme 150

Scheme 151

Scheme 152

1. CHECK MIL Check that the Malfunction Indicator Lamp (MIL) illuminates when turning the power switch on (IG). OK MIL lights up. NG --> See step 2 OK --> See step 11
2. CHECK CONNECTION BETWEEN TECHSTREAM AND ECM Connect the Techstream to the DLC3. Turn the power switch on (IG). Turn the Techstream on. Check the communication between the Techstream and ECM. Result Result Proceed to Communication is possible A Communication is not possible B A --> See step 12 B: Go to next step
3. CHECK MIL (THROTTLE POSITION SENSOR) Disconnect the throttle position sensor connector. Turn the power switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B Reconnect the throttle position sensor connector. A --> See step 13 B: Go to next step
4. CHECK MIL (CAMSHAFT POSITION SENSOR) Disconnect the camshaft position sensor connector. Turn the power switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B Reconnect the camshaft position sensor connector. A --> See step 14 B: Go to next step
5. CHECK MIL (MANIFOLD ABSOLUTE PRESSURE SENSOR) Disconnect the manifold absolute pressure sensor connector. Turn the power switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B Reconnect the manifold absolute pressure sensor connector. A --> See step 15 B: Go to next step
6. CHECK MIL (CANISTER PUMP MODULE) Disconnect the canister pump module connector. Turn the power switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B Reconnect the canister pump module connector. A --> See step 16 B: Go to next step
7. CHECK HARNESS AND CONNECTOR (THROTTLE POSITION SENSOR - ECM) Disconnect the throttle position sensor connector. Disconnect the ECM connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition D28-88 (VCTA) or D4-5 (VC) - Body ground Always 10 kohms or higher Callouts For see scheme 90 *1 Front view of wire harness connector (to Throttle Position Sensor) *2 Front view of wire harness connector (to ECM) Reconnect the throttle position sensor connector. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (THROTTLE POSITION SENSOR - ECM) OK: Go to next step
8. CHECK HARNESS AND CONNECTOR (CAMSHAFT POSITION SENSOR - ECM) Disconnect the camshaft position sensor connector. Disconnect the ECM connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition D18-3 (VC) or D28-99 (VCV1) - Body ground Always 10 kohms or higher Callouts For see scheme 91 *1 Front view of wire harness connector (to Camshaft Position Sensor) *2 Front view of wire harness connector (to ECM) Reconnect the camshaft position sensor connector. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (CAMSHAFT POSITION SENSOR - ECM) OK: Go to next step
9. CHECK HARNESS AND CONNECTOR (MANIFOLD ABSOLUTE PRESSURE SENSOR - ECM) Disconnect the manifold absolute pressure sensor connector. Disconnect the ECM connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition D3-3 (VC) or D28-72 (VCPM) - Body ground Always 10 kohms or higher Callouts For see scheme 92 *1 Front view of wire harness connector (to Manifold Absolute Pressure Sensor) *2 Front view of wire harness connector (to ECM) Reconnect the manifold absolute pressure sensor connector. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (MANIFOLD ABSOLUTE PRESSURE SENSOR - ECM) OK: Go to next step
10. CHECK HARNESS AND CONNECTOR (CANISTER PUMP MODULE - ECM) Disconnect the canister pump module connector. Disconnect the ECM connector. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition S16-6 (VCC) or D28-113 (VCPP) - Body ground Always 10 kohms or higher Callouts For see scheme 93 *1 Front view of wire harness connector (to Canister Pump Module) *2 Front view of wire harness connector (to ECM) Reconnect the canister pump module connector. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (CANISTER PUMP MODULE - ECM) OK --> See step 17
11. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE»(ref-393183-S00495152322011040700000)
12. GO TO MIL CIRCUIT. Refer to «MIL Circuit»(ref-393184-S26344047072011040700000)
13. REPLACE THROTTLE BODY ASSEMBLY. Refer to «REMOVAL»(ref-393185-S27458206012011040700000)
14. REPLACE CAMSHAFT POSITION SENSOR. Refer to «REMOVAL»(ref-393185-S22544630162011040700000)
15. REPLACE MANIFOLD ABSOLUTE PRESSURE SENSOR. Refer to «REMOVAL»(ref-393178-S01480003242011040700000)
16. REPLACE CANISTER. Refer to «REMOVAL»(ref-393178-S22090145052011040700000)
17. REPLACE ECM. Refer to «REMOVAL»(ref-393185-S12311789002011040700000)

When the NE signal is input to the ECM, Tr is turned on, current flows to the coil of the circuit opening relay, the relay switches on, power is supplied to the fuel pump and the fuel pump operates.

While the NE signal is generated (engine running), the ECM keeps Tr on (circuit opening relay on) and the fuel pump also keeps operating.

Scheme 153

Scheme 154

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

Scheme 155

Scheme 156

Scheme 157

Scheme 158

1. CHECK FUEL INJECTOR ASSEMBLY (POWER SOURCE) Disconnect the fuel injector assembly connectors. Turn the power switch on (IG). Measure the voltage according to the value(s) in the table below. Standard Voltage Tester Connection Switch Condition Specified Condition D14-1 - Body ground Power switch on (IG) 11 to 14 V D15-1 - Body ground Power switch on (IG) 11 to 14 V D16-1 - Body ground Power switch on (IG) 11 to 14 V D17-1 - Body ground Power switch on (IG) 11 to 14 V Callouts For (Scheme 152) *1 Front view of wire harness connector (to Fuel Injector Assembly) Reconnect the fuel injector assembly connectors. NG --> See step 4 OK: Go to next step
2. INSPECT FUEL INJECTOR ASSEMBLY Inspect the fuel injector assembly. Refer to «INSPECTION»(/toyota/prius/iii-2009-2011/remont/fuel-system/#engine-fuel-system-service-information-except-phv). NG --> See step 5 OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (FUEL INJECTOR ASSEMBLY - ECM) Disconnect the fuel injector assembly connectors. Disconnect the ECM connector. Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Open) Tester Connection Condition Specified Condition D14-2 - D28-85 (#10) Always Below 1 ohms D15-2 - D28-84 (#20) Always Below 1 ohms D16-2 - D28-83 (#30) Always Below 1 ohms D17-2 - D28-82 (#40) Always Below 1 ohms Standard Resistance (Check for Short) Tester Connection Condition Specified Condition D14-2 or D28-85 (#10) - Body ground Always 10 ohms or higher D15-2 or D28-84 (#20) - Body ground Always 10 ohms or higher D16-2 or D28-83 (#30) - Body ground Always 10 ohms or higher D17-2 or D28-82 (#40) - Body ground Always 10 ohms or higher Callouts For (Scheme 153) *1 Front view of wire harness connector (to Fuel Injector Assembly) *2 Front view of wire harness connector (to ECM) Reconnect the fuel injector assembly connectors. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (FUEL INJECTOR ASSEMBLY - ECM) OK --> See step 6
4. CHECK HARNESS AND CONNECTOR (INTEGRATION RELAY (IG2 RELAY) - FUEL INJECTOR ASSEMBLY) Disconnect the fuel injector assembly connectors. Remove the integration relay from the engine room relay block. Disconnect the integration relay connector. Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Open) Tester Connection Condition Specified Condition D14-1 - 1A-4 Always Below 1 ohms D15-1 - 1A-4 Always Below 1 ohms D16-1 - 1A-4 Always Below 1 ohms D17-1 - 1A-4 Always Below 1 ohms Standard Resistance (Check for Short) Tester Connection Condition Specified Condition D14-1 or 1A-4 - Body ground Always 10 kohms or higher D15-1 or 1A-4 - Body ground Always 10 kohms or higher D16-1 or 1A-4 - Body ground Always 10 kohms or higher D17-1 or 1A-4 - Body ground Always 10 kohms or higher Callouts For (Scheme 154) *1 Front view of wire harness connector (to Fuel Injector Assembly) *2 Integration Relay *3 Front view of wire harness connector (to Integration Relay) - - Reconnect the fuel injector assembly connectors. Reconnect the integration relay connector. Reinstall the integration relay. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (INTEGRATION RELAY (IG2 RELAY) - FUEL INJECTOR ASSEMBLY) OK --> See step 7
5. REPLACE FUEL INJECTOR ASSEMBLY. Refer to «REMOVAL»(/toyota/prius/iii-2009-2011/remont/fuel-system/#engine-fuel-system-service-information-except-phv)
6. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE»(ref-393183-S00495152322011040700000)
7. CHECK ECM POWER SOURCE CIRCUIT. Refer to «ECM Power Source Circuit»(ref-393184-S23344827292011040700000)

The MIL (Malfunction Indicator Lamp) is used to indicate vehicle malfunction detected by the ECM. When the power switch is turned on (IG), 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 power switch is first turned on (IG), the MIL should illuminate and should then turn off. If the MIL remains illuminated or is not illuminated, conduct the following troubleshooting procedure using the Techstream.

Scheme 159

Scheme 160

Scheme 161

1. CHECK THAT MIL IS ILLUMINATED Turn the power switch on (IG). Check the illumination of the MIL. Result Condition Proceed to MIL remains illuminated (Even after power switch is turned on (IG) and several seconds have passed, MIL still remains illuminated) A MIL remains off (Does not illuminate at all) B MIL illuminates for several seconds, but turns off after engine is started C C --> SYSTEM OK B --> See step 5 A: Go to next step
2. CHECK WHETHER MIL TURNS OFF Connect the Techstream to the DLC3. Turn the power switch on (IG). Turn the Techstream on. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes. Check if any DTCs have been stored. Note down the DTCs. Clear the DTCs. Refer to «DTC CHECK / CLEAR»(ref-393183-S13119469612011040700000). Check if the MIL goes off. OK MIL goes off. NG --> See step 3 OK --> See step 8
3. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT IN WIRE HARNESS) Disconnect the ECM connector. *1 Front view of wire harness connector (to ECM) Turn the power switch on (IG). Check that the MIL is not illuminated. OK MIL is not illuminated. Reconnect the ECM connector. NG --> See step 4 OK --> See step 9
4. CHECK HARNESS AND CONNECTOR (NO. 3 METER CIRCUIT PLATE - ECM) Disconnect the No. 3 meter circuit plate connector. Disconnect the ECM connector. Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Short) Tester Connection Condition Specified Condition L27-25 (EFI) or A57-36 (W) - Body ground Always 10 kohms or higher Callouts For see scheme 107 *1 Front view of wire harness connector (to No. 3 Meter Circuit Plate) *2 Front view of wire harness connector (to ECM) Reconnect the No. 3 meter circuit plate connector. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (NO. 3 METER CIRCUIT PLATE - ECM) OK --> See step 10
5. CHECK THAT ENGINE STARTS Turn the power switch on (IG). Put the engine in inspection mode. Refer to «INSPECTION MODE PROCEDURE»(ref-393046-S20890913792011040700000). Start the engine. Result Result Proceed to Engine starts A Engine cannot be put in inspection mode* (Engine cannot start) B HINT: *: The Techstream cannot communicate with the ECM. B --> See step 11 A: Go to next step
6. CHECK HARNESS AND CONNECTOR (ECM TERMINAL VOLTAGE) Disconnect the ECM connector. Turn the power switch on (IG). Measure the voltage according to the value(s) in the table below. Standard Voltage Tester Connection Switch Condition Specified Condition A57-36 (W) - Body ground Power switch on (IG) 11 to 14 V Callouts For see scheme 108 *1 Front view of wire harness connector (to ECM) NG --> See step 7 OK --> See step 9
7. CHECK HARNESS AND CONNECTOR (NO. 3 METER CIRCUIT PLATE - ECM) Disconnect the No. 3 meter circuit plate connector. Disconnect the ECM connector. Measure the resistance according to the value(s) in the table below. Standard Resistance (Check for Open) Tester Connection Condition Specified Condition L27-25 (EFI) - A57-36 (W) Always Below 1 ohms Callouts For see scheme 109 *1 Front view of wire harness connector (to No. 3 Meter Circuit Plate) *2 Front view of wire harness connector (to ECM) Reconnect the ECM connector. Reconnect the No. 3 meter circuit plate connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (NO. 3 METER CIRCUIT PLATE - ECM) OK --> See step 10
8. REPAIR CIRCUITS INDICATED BY OUTPUT DTCS. Refer to «DIAGNOSTIC TROUBLE CODE CHART»(ref-393183-S20320380732011040700000)
9. REPLACE ECM. Refer to «REMOVAL»(ref-393185-S12311789002011040700000)
10. REPLACE NO. 3 METER CIRCUIT PLATE. Refer to «DISASSEMBLY»(ref-393196-S11617508282011040700000)
11. GO TO VC OUTPUT CIRCUIT. Refer to «VC Output Circuit»(ref-393184-S09514942552011040700000)

See also:
• ON-VEHICLE INSPECTION
• ON-VEHICLE INSPECTION - Step 2
• INSPECTION