STEP 1. Check harness connector B-26 at ECM for damage.
STEP 2. Measure the output voltage at ECM connector B-26 by using power plant ECU check harness special tool MB992110.
(1) Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.
(2) Start the engine and run at idle.
(3) Measure the voltage between terminal No. 61 and ground.note | Vehicles for Canada, the headlight, taillight, etc. remain lit even when the lighting switch is in "OFF" position but this is no problem for checks. |
- Engine: warming up
- Radiator fan: stopped
- Headlight switch: OFF to ON
- Rear defogger switch: OFF to ON
- Stoplight switch: OFF to ON
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Did the measured voltage drop?
Go to Step 3. Go to Step 4.
STEP 3. Using scan tool MB991958, read the diagnostic trouble code (DTC).
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) Start the engine and run at idle.
(3) After the DTC has been deleted, read the DTC again.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is DTC P0622 set?
Replace the ECM (Refer to, Removal and Installation ). Then go to Step 8. It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
STEP 4. Check harness connector B-117 at generator for damage.
STEP 5. Measure the power supply voltage at generator harness side connector B-117.
(1) Disconnect the connector B-117 and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal No. 4 and ground.- Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 7. Go to Step 6.
STEP 6. Check for open circuit between generator connector B-117 (terminal No. 4) and ECM connector B-26 (terminal No. 61).
STEP 7. Check for harness damage between generator connector B-117 (terminal No. 4) and ECM connector B-26 (terminal No. 61).
STEP 8. Using scan tool MB991958, read the diagnostic trouble code (DTC).
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) Start the engine and run at idle.
(3) After the DTC has been deleted, read the DTC again.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is DTC P0622 set?
Retry the troubleshooting. The inspection is complete.