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Inspection procedure 22: Generator output voltage is low (approximately 12.8 volts).
 
 
 
 
CIRCUIT OPERATION
  • The ECM controls generator output current by duty-controlling continuity between the generator G terminal and ground.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this charging system: )
  • Charging system failed.
  • Shorted generator G terminal circuit.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tool:
  • MB992110: Power Plant ECU Check Harness
STEP 1. Measure the voltage at ECM connector 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 ALTG and ground.
noteVehicle for Canada, the headlight, taillight, etc. remain lit even when the lighting switch is in "OFF" position but this is no problem for checks.
  1. Engine: warming up, idling
  2. Radiator fan: stopped
  3. Headlight: OFF to ON
  4. Stop light: OFF to ON
  5. Rear defogger switch: OFF to ON
  • Voltage should increases
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Did the measured voltage increase?
Go to Step 2.
Replace the generator. Then confirm that the malfunction symptom is eliminated.
 
STEP 2. Check of short circuit to ground in ALTG line between generator connector and ECM connector.
Is the harness wire in good condition?
Replace the ECM (Refer to, Removal and Installation ). Then confirm that the malfunction symptom is eliminated.
Repair it. Then confirm that the malfunction symptom is eliminated.