Alternator Control Circuit Troubleshooting

Alternator Control Circuit Troubleshooting

1. Check for proper operation of the electrical toad detector (ELD) by checking for a DTC. If a DTC is present, diagnose and repair the cause before continuing with this test.

NOTE: The ELD DTC does not turn on The MIL.

2. Disconnect the alternator 4P connector from the alternator.
3. Start the engine, and turn on the headlights to high beam.




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

Is there less than 1 V?

YES - Go to step 13.

NO - Go to step 5.

5. Turn off the headlights, and turn the ignition switch to LOCK (0).
6. Connect the Honda Diagnostic System (HDS) to the data link connector (DLC).
7. Turn the ignition switch to ON (II).
8. Make sure the HDS communicates with the vehicle and the engine control module (ECM). If it doesn't communicate, troubleshoot the DLC circuit.
9. Jump the SCS line with the HDS.

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

10. Turn the ignition switch to LOCK (0).
11. Disconnect the ECM connector B (24P).




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

Is there continuity?

YES - Repair short to ground in the wire between the alternator and the ECM (B18).

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

13. Turn off the headlights, and turn the ignition switch to LOCK (0).
14. Connect the HDS to the DLC.
15. Turn the ignition switch to ON (II).
16. Make sure the HDS communicates with the vehicle and the ECM. If it doesn't communicate, troubleshoot the DLC circuit.
17. Jump the SCS line with the HDS.

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

18. Turn the ignition switch to LOCK (0).
19. Disconnect the ECM connector B (24P).




20. Check for continuity between the ECM connector terminal B18 and alternator 4P connector terminal No. 2.

Is there continuity?

YES - Replace the alternator or repair the alternator.

NO - Repair open in the wire between the alternator and ECM (B18).