A/C Signal Circuit Troubleshooting
A/C Signal Circuit Troubleshooting1. 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. 5V?
YES - Go to step 5.
NO - Go to step ~2.
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 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 the ECM/PCM (A27) and the A/C pressure switch.
NO - Substitute a known-good ECM/PCM and recheck. If the prescribed voltage is now available, replace the original ECM/PCM. If not, check the A/C system for other symptoms.
15. Momentarily connect under-hood fuse/relay box 16 P connector terminal No.11 to body ground with a jumper wire several times.
NOTE: The under-hood fuse/relay box 16P connector is on the bottom of the fuse box. When you unbolt and invert the fuse box, leave the upper cover on to prevent short circuits.
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 terminals 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.
NO - Repair open in the wire between the ECM/PCM (A27) and the A/C pressure switch.