A/C Signal Circuit Troubleshooting

A/C Signal Circuit Troubleshooting

1. Start the engine, and let it idle.

2. Turn the blower switch on.

3. Turn the A/C switch on.

4. Check the A/C CLUTCH in the DATA LIST with the HDS.

Does it indicate ON?
YES - Go to step 5.

NO - Do the A/C system test. A/C System Test (With A/C)


5. Check the A/C system.

Does the A/C system operate?
YES - The air conditioning signal circuit is OK.

NO - Go to step 6.


6. Turn the ignition switch to LOCK (0).

7. Turn the ignition switch to ON (II).

8. 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. A/C System Test (With A/C)

NO - Go to step 9.


9. Turn the ignition switch to LOCK (0).

10. Jump the SCS line with the HDS.

11. Disconnect ECM/PCM connector A (44P).

12. Turn the ignition switch to ON (II).

13. Momentarily connect ECM/PCM connector terminal A14 to body ground with a jumper wire several times.

Is there a clicking noise from the A/C compressor clutch?
YES - Update the ECM/PCM if it does not have the latest software, ECM/PCM Update (A/T) or substitute a known-good ECM/PCM, Initial Inspection and Diagnostic Overview then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM. Service and Repair

NO - Check for poor connections or loose terminals at the A/C clutch relay and the ECM/PCM. If the connections and the terminals are OK, check the A/C clutch relay. Power Relay Test If needed, repair open in the wire between the ECM/PCM (A14), the A/C compressor clutch relay, and other A/C system parts.