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
- Turn the ignition switch OFF.
- Disconnect the A/C pressure switch connector.
- Turn the ignition switch ON (II).
- Measure voltage between ECM connector terminals A27 and B20.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there about 5 V?
- YES - Go to step 5.
- NO - Go to step 12.
- Turn the ignition switch OFF.
- Reconnect the A/C pressure switch connector.
- Turn the ignition switch ON (II).
- Momentarily connect ECM connector terminals A17 and B20 with a jumper wire several times.
Is there a clicking noise from the A/C compressor clutch?
- YES - Go to step 9.
- NO - Go to step 15.
- Start the engine.
- Turn the blower switch ON.
- Turn the A/C switch ON.
Does the A/C operate?
- YES - The air conditioning signal is OK.
- NO - Go to step 16.
- Turn the ignition switch OFF.
- Disconnect ECM connector A (32P).
- Check for continuity between body ground and ECM connector terminal A27.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
- YES - Repair short in the wire between the ECM (A27) and the A/C pressure switch.
- NO - Substitute a known-good ECM (see HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES ) and recheck. If voltage is now normal, replace the original ECM (see ECM REPLACEMENT ). If not, check the A/C system for other symptoms.
- Momentarily connect main under-hood fuse/relay box 16P connector terminal No. 11 to body ground with a jumper wire several times.NOTE: The main under-hood fuse/relay box 14P connector is on the bottom of the fuse box. When you unbolt and invert the fuse box, leave the upper cover on it to prevent short circuits.
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.
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