Alternator Control Circuit Troubleshooting

Alternator Control Circuit Troubleshooting

1. Check for proper operation of the electrical load 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. Connect the Honda Diagnostic System (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.
3. Disconnect the alternator 4P connector from the alternator.
4. Start the engine, and turn on the headlights to high beam.




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

Is there 1 V or less?

YES - Go to step 9.

NO - Go to step 6.

6. Jump the SCS line with the HDS, then turn the ignition switch OFF.

NOTE: This step must be done to protect the engine control module (ECM)/powertrain control module (PCM) from damage.

7. Disconnect ECM/PCM connector E (31P) (2004-2005 models) or A (31P) (2006 model).




8. Check for continuity between ECM/PCM connector terminal E24 (2004-2005 models) or A24 (2006 model) and body ground.

Is there continuity?

YES - Repair a short to body ground in the wire between the alternator and the ECM/PCM (E24 (2004-2005 models) or A24 (2006 model)).

NO - Update the ECM/PCM if it does not have the latest software, 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.

9. Jump the SCS line with the HDS, then turn the ignition switch OFF.

NOTE: This step must be done to protect the engine control module (ECM)/powertrain control module (PCM) from damage.

10. Disconnect ECM/PCM connector E (31P) (2004-2005 models) or A (31P) (2006 model).




11. Check for continuity between ECM/PCM connector terminal E24 (2004-2005 models) or A24 (2006 model) and body ground.

Is there continuity?

YES - Replace the alternator or repair the alternator

NO - Repair an open in the wire between the alternator and the ECM/PCM (E24 (2004-2005 models) or A24 (2006 model)).