Alternator Control Circuit Troubleshooting
- Connect the HDS to the data link connector (DLC), and check for DTCs. If a DTC is present, diagnose and repair the cause before continuing with this test.
- Disconnect the alternator 4P connector from the alternator.
- Start the engine, and turn on the headlights to high beam.
- Measure the voltage between alternator 4P connector terminal No. 2 and the positive terminal of the battery.
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Is there 1 V or less?
YES -Go to step 5.
NO -Go to step 8.
- Jump the SCS line with the HDS, then turn the ignition switch OFF.NOTE: This step must be done to protect the powertrain control module (PCM) from damage.
- Disconnect PCM connector A (31P).
- Check for continuity between PCM connector terminal A24 and body ground.
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Is there continuity?
YES -Repair short in the wire between the alternator and the PCM.
NO -Update the PCM if it does not have the latest software (see UPDATING THE PCM ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM (see PCM REPLACEMENT ).
- Jump the SCS line with the HDS, then turn the ignition switch OFF.NOTE: This step must be done to protect the PCM from damage.
- Disconnect PCM connector A (31P).
- Check for continuity between PCM connector terminal A24 and alternator 4P connector terminal No. 2.Fig 3: Checking Continuity Between PCM Connector Terminal A24 And Alternator 4P Connector Terminal 2
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Is there continuity?
YES -Replace the alternator (see ALTERNATOR REMOVAL AND INSTALLATION ), or repair the alternator (see ALTERNATOR OVERHAUL ).
NO -Repair open in the wire between the alternator and the PCM.