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Alternator Control Circuit Troubleshooting

  1. Turn the ignition switch to ON (II).
  1. Check for DTCs. If a DTC is present, diagnose and repair the cause before continuing with this test.
  1. Disconnect the alternator 4P connector from the alternator.
  1. Start the engine, and turn on the headlights to high beam.
  1. Measure the voltage between alternator 4P connector terminal No. 2 and the positive terminal of the battery.
Is there 1 V or less?
YES -
Go to Step 11 .
NO -
Go to Step 8 .
  1. Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0).
    NOTE: This step must be done to protect the ECM/PCM from damage.
  1. Disconnect ECM/PCM connector B (49P).

  1. Check for continuity between ECM/PCM connector terminal B45 and body ground.
Is there continuity?
YES -
Repair short in the wire between the alternator and the ECM/PCM.■
NO -
  1. Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0).
    NOTE: This step must be done to protect the ECM/PCM from damage.
  1. Disconnect ECM/PCM connector B (49P).

  1. Check for continuity between ECM/PCM connector terminal B45 and alternator 4P connector terminal No. 2.
Is there continuity?
YES -
NO -
Repair open in the wire between the alternator and the ECM/PCM.■