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), or press the engine start/stop button to select the OFF mode
- Jump the SCS line with the HDS
- Disconnect the alternator 4P connector
- Disconnect PCM connector C (49P)
- Check for continuity between PCM connector terminal C44 and body ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
YES -Repair short in the wire between the PCM (C44) and the alternator
NO -Update the PCM if it does not have the latest software (see ECM/PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE ECM/PCM ), then recheck If the symptom/indication goes away with a known-good PCM, replace the original PCM (see ECM/PCM REPLACEMENT )
Use the Manual With the Right Hardware
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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.