Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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?
YES -The alternator signal circuit is OK.
NO -Go to step 4.
- Turn the headlight switch off, and turn the ignition switch to LOCK (0).
- Jump the SCS line with the HDS.
- Disconnect the alternator 4P connector.
- Disconnect PCM connector B (49P).
- Check for continuity between PCM connector terminal B47 and body ground.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -Repair a short in the wire between the PCM (B47) and the alternator.
NO -Update the PCM if it does not have the latest software (see PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM (see PCM REPLACEMENT ).
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.