Alternator Control Circuit Troubleshooting

Alternator Control Circuit Troubleshooting

NOTE: Do this troubleshooting if, in step 5 of the alternator and regulator circuit troubleshooting Alternator and Regulator Circuit Troubleshooting, the battery voltage is less than 13.3 V.

1. Remove the engine compartment covers Service and Repair.

2. Connect the HDS to the DLC.

3. Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.

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

5. Check for DTCs Initial Inspection and Diagnostic Overview. If a DTC is present, diagnose and repair the cause before continuing with this test.

6. Disconnect the alternator 4P connector.

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

8. 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 12.

NO -

Go to step 9.

9. Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

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

10. Disconnect ECM/PCM connector C (49P).

11. Check for continuity between ECM/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 ECM/PCM connector terminal C43.�

NO -

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

12. Jump the SCS line with the HDS, then turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.

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

13. Disconnect ECM/PCM connector C (49P).

14. Check for loose terminals and connectors, then check for continuity between ECM/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 open in the wire between alternator 4P connector terminal No. 2 and ECM/PCM connector terminal C43.�

15. Install the engine compartment covers Service and Repair.