Alternator Control Circuit Troubleshooting
- Connect the Honda Diagnostic System (HDS) to the data link connector (DLC) (see step 2 in HOW TO USE THE HDS (HONDA DIAGNOSTIC SYSTEM) ).
- Turn the ignition switch ON (II).
- Make sure the HDS communicates with the vehicle and the engine control module (ECM)/powertrain control module (PCM). If it doesn't communicate, troubleshoot the DLC circuit (see DLC CIRCUIT TROUBLESHOOTING ).
- Check for DTCs (see GENERAL TROUBLESHOOTING INFORMATION ). If a DTC is present, diagnose and repair the cause before continuing with this test.
- Disconnect the alternator 4P connector from the alternator.
- Start the engine, and turn on the headlights to high beam.
- 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 11.
NO - Go to step 8.
- Jump the SCS line with the HDS, then turn the ignition switch OFF.NOTE: This step must be done to protect the ECM/PCM from damage.
- Disconnect ECM/PCM connector B (24P).
- Check for continuity between ECM/PCM connector terminal B18 and body ground.
Is there continuity?
YES - Repair short in the wire between the alternator and the ECM/PCM.
NO - Update the ECM/PCM if it does not have the latest software (see UPDATING THE ECM/PCM ), or substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ), then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ).
- Jump the SCS line with the HDS, then turn the ignition switch OFF.NOTE: This step must be done to protect the ECM/PCM from damage.
- Disconnect ECM/PCM connector B (24P).
- Check for continuity between ECM/PCM connector terminal B18 and alternator 4P connector terminal No. 2.
Is there continuity?
YES - Replace the alternator (see ALTERNATOR REMOVAL AND INSTALLATION ), or repair the alternator (see ALTERNATOR OVERHAUL ).
NO - Repair open in the wire between the alternator and the ECM/PCM.