Inspection Procedure 26

INSPECTION PROCEDURE 26: Generator output voltage is low (approximately 12.3 volts).

Generator Circuit:

CIRCUIT OPERATION
- The ECM or the PCM controls generator out put current by duty-controlling continuity between the generator G terminal (terminal No. 1) and ground.

TROUBLESHOOTING HINTS (The most likely causes for this charging system:)
- Malfunction of the charging system.
- Short circuit in harness between generator G terminal and ECM or PCM .
- ECM failed.
- PCM failed.

DIAGNOSIS

Required Special Tool:
- MB991923: Power Train ECU Check Harness

STEP 1. Measure the voltage at ECM or PCM connector B-22 by using check harness special tool MB991923.

1. Disconnect all ECM connectors or PCM connectors. Connect the check harness special tool MB991923 between the separated connectors.
2. Start the engine and run at idle.

3. Measure the voltage between terminal No. 132 and ground.

NOTE: Vehicle for Canada, the headlight, taillight, etc. remain lit even when the lighting switch is in "OFF" position but this is no problem for checks.
a. Engine: warming up
b. Radiator fan: stopped
c. Headlight switch: OFF to ON
d. Rear defogger switch: OFF to ON
e. Stoplight switch: OFF to ON
- Voltage rises.

4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the measured voltage within the specified range?

YES: Go to Step 2.

NO: Replace the generator. Then confirm that the malfunction symptom is eliminated.

STEP 2. Check harness connector B-22 at ECM or PCM connector and harness connector B-120 at generator connector for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 3.

NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.

STEP 3. Check for open circuit and short circuit to ground and harness damage between generator connector B-120 (terminal No. 1) and ECM or PCM connector B-22 (terminal No. 132).

Q: Is the harness wire in good condition?

YES: Replace the ECM or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Refer to Encrypted Code Registration Criteria Table in Antitheft and Alarm Systems. Then confirm that the malfunction symptom is eliminated.

NO: Repair it. Then confirm that the malfunction symptom is eliminated.