Alternator Control Circuit Troubleshooting

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. 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 1 V or less?
YES | - | Go to Step 5 .
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 engine control module (ECM)/powertrain control module (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 a short in the wire between the alternator and the 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. ■
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. 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 or repair the alternator. ■
NO | - | Repair an open in the wire between the alternator and the ECM/PCM.■