Air Conditioning Signal

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 A27 and B20.
Is there approx. 5 V?
YES-Go to step 5.
NO-Go to step 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 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.
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.
NO-Go to step 16.
12. Turn the ignition switch OFF.
13. Disconnect the ECM/PCM connector A (32P)




14. Check for continuity between body ground and ECM/PCM connector terminal A27.
Is there continuity?
YES-Repair short in the wire between ECM/PCM (A27) and the A/C pressure switch.
NO-Substitute a known-good ECM/PCM and recheck. If prescribed voltage is now available, replace the original ECM/PCM. If not, check the A/C system for other symptoms.
Diagnostic Strategies




15. Momentarily connect the under-hood fuse/relay box 16p connector terminal No.11 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 (A17) and the A/C clutch relay.
NO-Check the A/C system for other symptoms.




16. Measure voltage between ECM/PCM connector terminal A27 and B20.
Is there less than 1.0 V?
YES-Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original ECM/PCM. If not, inspect the air conditioning system.
Diagnostic Strategies

NO-Repair open in the wire between the ECM/PCM (A27) and the A/C pressure switch.