Inspection Procedure 3
The Malfunction Indicator Lamp (SERVICE ENGINE SOON or Check Engine Lamp) Does Not Illuminate Right after the Ignition Switch Is Turned to the "ON" Position.Malfunction Indicator Lamp (Service Engine Soon Or Check Engine Lamp) Circuit Part 1:
Malfunction Indicator Lamp (Service Engine Soon Or Check Engine Lamp) Circuit Part 2:
CIRCUIT OPERATION
- The malfunction indicator lamp (SERVICE ENGINE SOON or Check Engine Lamp) power is supplied from the ignition switch.
- The ECM
COMMENT
- The ECM
TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Burnt-out bulb.
- Defective malfunction indicator lamp (SERVICE ENGINE SOON or Check Engine Lamp) circuit.
- Malfunction of the ECM
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (MUT-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 be battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the voltage normal?
YES: Go to Step 2.
NO: Refer to INSPECTION PROCEDURE 29 - Power Supply System and Ignition Switch - IG System.
STEP 2. Check the burned-out bulb.
Q: Is the valve normal?
YES: Go to step 3.
NO: Replace the bulb. Then confirm that the malfunction symptom is eliminated.
STEP 3. Check connector C-41 at the combination meter for damage.
Q: Is the connector in good condition?
YES: Go to step 4.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 4. Check the power supply voltage at combination meter harness side connector C-41.
1. Disconnect the connector C-41 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 52 and ground.
- Voltage should be 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-108 and C-111 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connectors are in good condition, repair harness wire between ignition switch connector C-87 (terminal No. 2) and combination meter connector C-41 (terminal No. 52) because of open circuit. Then confirm that the malfunction symptom is eliminated.
STEP 5. Check connector C-51 at ECM
Q: Is the connector in good condition?
YES: Go to Step 6.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 6. Check the power supply voltage ECM connector C-51
1. Disconnect the connector C-51
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 22 and ground.
- Voltage should be 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 or PCM. Then confirm that the malfunction symptom is eliminated.
NO: Check harness connectors C-28 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connectors is in good condition, repair harness wire between combination meter connector C-41 terminal 41 and ECM connector C-51 (terminal No. 22)