Alternator Control Circuit Troubleshooting

Alternator Control System Test

1. Check for proper operation of the electrical load detector (ELD) by checking the malfunction indicator lamp (MIL).
2. Connect the Honda Diagnostic System (HDS) to the data link connector (DLC), and check for DTC's. 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 the headlights ON to high beam.




5. Measure 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 6.

NO - Go to step 9.

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 engine control module ECM/PCM connector B (24P).




8. Check for continuity between ECM/PCM connector terminal B18 and body ground.

Is there continuity?

YES Repair a short in the wire between the alternator and ECM/PCM.

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) for damage.

10. Disconnect ECM/PCM connector B (24P).




11. Check for continuity between ECM/PCM connector terminal B18 and alternator 4P connector terminal No.2.

Is there continuity?

YES - Replace or repair the alternator.

NO - Repair an open in the wire between the alternator and ECM/PCM.