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 SYSTEM INSPECTION )
- 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 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 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 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 )
NO -Check for poor connections or loose terminals at the A/C clutch relay and the 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 PCM (A13), the A/C clutch relay, and 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.