Alternator FR Signal Circuit Troubleshooting

Start the engine, and let it idle.
Monitor the ALTERNATOR in the DATA LIST with the HDS.
Check if the indicated percentage varies when the headlight switch is turned on.
Does the percentage vary?
1. YES - The alternator signal circuit is OK.
2. NO - Go to step 4.
Turn the headlight switch and ignition switch OFF.
Jump the SCS line with the HDS.
Disconnect the alternator 4P connector.
Disconnect ECM/PCM connector B (24P).
Check for continuity between body ground and ECM/PCM connector terminal B13.

Fig 1: Checking Continuity Between Body Ground And ECM/PCM Connector Terminal B13
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Repair short in the wire between the ECM/PCM (B13) and the alternator.
2. NO - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM (see ECM/PCM UPDATING AND SUBSTITUTION FOR TESTING ), then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ).