Alternator Control Circuit Troubleshooting

Alternator Control Circuit Troubleshooting

NOTE: Do this troubleshooting if, in step 4 of the alternator and regulator circuit troubleshooting Alternator and Regulator Circuit Troubleshooting, the battery voltage is less than 13.5 V.

1. Connect the HDS to the DLC.

2. Turn the ignition switch to ON (II).

3. Make sure the HDS communicates with the vehicle and the PCM. If it does not communicate, troubleshoot the DLC circuit Testing and Inspection.

4. Check for DTCs. If a DTC is present, diagnose and repair the cause before continuing with this test.

5. Disconnect the alternator 4P connector.

6. Start the engine, and turn on the headlights to high beam.

7. Measure the voltage between alternator 4P connector terminal No. 2 and the positive terminal of the battery.





Is there less than 1 V?

YES -

Go to step 11.

NO -

Go to step 8.

8. Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0).

NOTE: This step must be done to protect the PCM from damage.

9. Disconnect PCM connector C (49P).

10. Check for continuity between PCM connector terminal C43 and body ground.





Is there continuity?

YES -

Repair a short to ground in the wire between alternator 4P connector terminal No. 2 and PCM connector terminal C43.�

NO -

Update the PCM if it does not have the latest software PCM Update, or substitute a known-good PCM, then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM Service and Repair.�

11. Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0).

NOTE: This step must be done to protect the PCM from damage.

12. Disconnect PCM connector C (49P).

13. Check for loose terminals and connections, then check for continuity between PCM connector terminal C43 and alternator 4P connector terminal No. 2.





Is there continuity?

YES -

Replace the alternator Removal and Replacement, or repair the alternator Overhaul.�

NO -

Repair an open in the wire between the alternator 4P connector terminal No. 2 and PCM connector terminal C43.�