## A/C Signal Circuit Troubleshooting

1. | Turn the ignition switch OFF.

2. | Disconnect the A/C pressure switch connector.

3. | Turn the ignition switch ON (II).

4. | Measure voltage between ECM/PCM connector terminals A24 and E28. Is there approx. 5 V? YES - Go to 5. NO - Go to 12.

5. | Turn the ignition switch OFF.

6. | Reconnect the A/C pressure switch connector.

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

8. | Momentarily connect ECM/PCM connector terminals A24 and E18 with a jumper wire several times. Is there a clicking noise from the A/C compressor clutch? YES - Go to 9. NO - Go to 15.

9. | Start the engine.

10. | Turn the blower switch ON.

11. | Turn the A/C switch ON. Does the A/C operate? YES - The air conditioning signal is OK.n NO - Go to 16.

12. | Turn the ignition switch OFF.

13. | Disconnect ECM/PCM connector E (31P).

14. | Check for continuity between body ground and ECM/PCM connector terminal E28. Is there continuity? YES - Repair short in the wire between the ECM/PCM (E28) and the A/C pressure switch.n NO - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.n

15. | Momentarily connect the A/C compressor clutch relay 4P connector (into the under-hood fuse/relay box) terminal No. 3 to body ground with a jumper wire several times. Is there a clicking noise from the A/C compressor clutch? YES - Repair open in the wire between the ECM/PCM (E18) and the A/C clutch relay.n NO - Check the A/C system for other symptoms.n

16. | Measure voltage between ECM/PCM connector terminals A24 and E28. Is there less than 1.0 V? YES - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.n NO - Repair open in the wire between the ECM/PCM (E28) and the A/C pressure switch.n