Inspection Procedure 4
Service Engine Soon/Malfunction Indicator Lamp Circuit:
CIRCUIT OPERATION
- The service engine soon/malfunction indicator lamp power is supplied from the ignition switch.
- The ECM or PCM controls the ground of the service engine soon/malfunction indicator lamp by turning the power transistor in the ECM or PCM ON and OFF.
COMMENT
- In cases such as the above, the cause is probably that the ECM or PCM is detecting a problem in a sensor or actuator, or that one of the malfunctions listed at right has probably occurred.
TROUBLESHOOTING HINTS
The most likely causes for this case:
- Short-circuit between the service engine soon/malfunction indicator lamp and ECM.
- Short-circuit between the service engine soon/malfunction indicator lamp and PCM.
- Malfunction of the ECM.
- Malfunction of the PCM.
DIAGNOSIS
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting the scan tool MB991502.
STEP 1. Using scan tool MB991502, read the diagnostic trouble code (DTC).
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to "ON" position.
3. Read the DTC.
If DTC is not output, go to Step 2.
If DTC is output, refer to Diagnostic Trouble Code Chart.
STEP 2. Check the circuit at combination meter connector C41.
1. Disconnect connector C-41 and measure at the harness side.
2. Disconnect the ECM connector C-51
3. Check for continuity between connector C-41 terminal 41 and ground.
- Should be open circuit.
If there is open circuit, replace the ECM or PCM. If there is less than 2 ohms , repair the harness wire between the combination meter connector C-41 and the ECM connector C-51
Then confirm that the malfunction symptom is eliminated.