Alternator Control Circuit Troubleshooting

Alternator Control Circuit Troubleshooting

'06-09 models

1. Disconnect the alternator 4P connector.

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

3. 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 4.






4. Turn off the headlights, and turn the ignition switch to LOCK (0).

5. Connect the Honda Diagnostic System (HDS) to the data link connector (DLC). Initial Inspection and Diagnostic Overview

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

7. Make sure the HDS communicates with the vehicle and the engine control module (ECM). If it does not communicate, troubleshoot the DLC circuit. Testing and Inspection

8. Jump the SCS line with the HDS.
NOTE: This step must be done to protect the ECM from damage.

9. Turn the ignition switch to LOCK (0).

10. Disconnect the ECM connector B (24P).

11. Check for continuity between ECM connector terminal B18 and body ground.

Is there continuity?
YES - Repair short to ground in the wire between alternator 4P connector terminal No. 2 and ECM connector terminal B18.

NO - Update the ECM if it does not have the latest software, ECM Update or substitute a known-good ECM, Initial Inspection and Diagnostic Overview then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM. Service and Repair






12. Turn off the headlights, and turn the ignition switch to LOCK (0).

13. Connect the HDS to the DLC. Initial Inspection and Diagnostic Overview

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

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

16. Jump the SCS line with the HDS.
NOTE: This step must be done to protect the ECM from damage.

17. Turn the ignition switch to LOCK (0).

18. Disconnect the ECM connector B (24P).

19. Check for continuity between ECM connector terminal B18 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 connector terminal B18.