Inspection Procedure 25

INSPECTION PROCEDURE 25: Generator output voltage is low (approximately 12.3 volts)

Generation Circuit (Part 1):

Generator Circuit (Part 2):

CIRCUIT OPERATION
- The ECM [M/T] or the PCM [A/T] 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 [M/T] or PCM [A/T].
- ECM failed. [M/T]
- PCM failed. [A/T]

DIAGNOSIS

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

STEP 1. Measure the voltage at ECM [M/T] or PCM [A/T] connector B-22 by using check harness special tool M B991923.










1. Disconnect all ECM [M/T] connectors or PCM [A/T] 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 [M/T] or PCM [A/T] 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 [M/T] or PCM [A/T] 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. Then confirm that the malfunction symptom is eliminated.

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