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


5. Check the A/C system.

Does the A/C system operate?
YES - The air conditioning system 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

NO - Go to step 9.


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

10. Jump the SCS line with the HDS.

11. Disconnect ECM connector A (44P).

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

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

Is there a clicking noise from the A/C compressor clutch?
YES - Reconnect all connectors, and update the ECM if it does not have the latest software, ECM/PCM Update or substitute a known-good ECM, Reading and Clearing Diagnostic Trouble Codes then recheck. If the symptom/indication goes away and the ECM was updated, troubleshooting is complete. If the symptom/indication goes away and the ECM was substituted, replace the original ECM. Service and Repair

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