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.
A/C Signal Circuit Troubleshooting
- Start the engine.
- Turn the blower switch on.
- Turn the A/C switch on.
- Check the A/C CLUTCH in the DATA LIST with the HDS.
Does it indicate ON?
YES - Go to step 5.
NO - Check the A/C system (see A/C SERVICE TIPS AND PRECAUTIONS ).
- Check the A/C system operation.
Does the A/C system operate?
YES - The air conditioning system circuit is OK.
NO - Go to step 6.
- Turn the ignition switch to LOCK (0), or press the engine start/stop button to select the OFF mode.
- Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.
- Activate the A/C CLUTCH in the INSPECTION MENU with the HDS.
Is there a clicking noise from the A/C compressor clutch?
YES - Do the A/C system test (see A/C SYSTEM TEST ).
NO - Go to step 9.
- 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 ECM/PCM connector A (49P).
- Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.
- Momentarily connect ECM/PCM connector terminal A13 to body ground with a jumper wire several times.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there a clicking noise from the A/C compressor clutch?
YES - Update the ECM/PCM if it does not have the latest software (see ECM/PCM UPDATE ), or substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ), then recheck. If the symptom/indication goes away and the ECM/PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the ECM/PCM was substituted, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ).
NO - Check for poor connections or loose terminals at the A/C clutch relay and the ECM/PCM. If the connections are OK, check the A/C clutch relay (see POWER RELAY TEST ). If needed, repair open in the wire between the ECM/PCM (A13) and the A/C clutch relay, and check the other A/C system parts.
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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.
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