Inspection Procedure 3
INSPECTION PROCEDURE 3: The Malfunction Indicator Lamp (SERVICE ENGINE SOON) Does Not Illuminate Right After The Ignition Switch is Turned to The "ON" PositionMalfunction Indicator Lamp (Service Engine Soon) Circuit Part 1:
Malfunction Indicator Lamp (Service Engine Soon) Circuit Part 2:
CIRCUIT OPERATION
- The malfunction indicator lamp (SERVICE ENGINE SOON) power is supplied from the ignition switch.
- The ECM controls the ground of the malfunction indicator lamp (SERVICE ENGINE SOON) by turning the power transistor in the ECM ON and OFF.
COMMENT
- The ECM causes the malfunction indicator lamp (SERVICE ENGINE SOON) to illuminate for 5 seconds immediately after the ignition switch is turned to the "ON" position occurred.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Burnt-out bulb.
- Defective malfunction indicator lamp (SERVICE ENGINE SOON) circuit.
- Malfunction of the ECM.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
STEP 1. Using scan tool MB991958, check data list item 16: Power Supply Voltage.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before. Connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991958 to the data reading mode for item 16, Power Supply Voltage.
- Voltage should measure battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 2.
NO: Refer to INSPECTION PROCEDURE 30 - Power Supply System and Ignition Switch - IG System.
STEP 2. Check the burned-out bulb.
Q: Is the bulb normal?
YES: Go to step 3.
NO: Replace the bulb. Then confirm that the malfunction symptom is eliminated.
STEP 3. Check connector C-01 at the combination meter for damage.
Q: Is the connector in good condition?
YES: Go to step 4.
NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 4. Measure the power supply voltage at combination meter harness side connector C-01.
1. Disconnect the connector C-01 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No.9 and ground.
- Voltage should measure battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Go to Step 5.
NO: Check harness connectors C-23, C-211 and C-214 at intermediate connector for damage, and repair or replace as required. If intermediate connectors are in good condition, repair harness wire between ignition switch connector C-208 (terminal No.2) and combination meter connector C-01 (terminal No.9) because of open circuit. Then confirm that the malfunction symptom is eliminated.
STEP 5. Check connector C-121 at ECM for damage.
Q: Is the connector in good condition?
YES: Go to Step 6.
NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 6. Measure the power supply voltage ECM connector C-121.
1. Disconnect the connector C-121 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No.22 and ground.
- Voltage should measure battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES: Replace the ECM. Then confirm that the malfunction symptom is eliminated.
NO: Check harness connectors C-124 at intermediate connector for damage, and repair or replace as required. If intermediate connectors is in good condition, repair harness wire between combination meter connector C-01 (terminal No.17) and ECM connector C-121 (terminal No.22) because of open circuit. Then confirm that the malfunction symptom is eliminated.