A/C Signal Circuit Troubleshooting
A/C Signal Circuit Troubleshooting1. Turn the ignition switch OFF.
2. Disconnect the A/C pressure switch 4P connector.
3. Turn the ignition switch ON (II).
4. Measure voltage between PCM connector terminals A27 and B20.
Is there about 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 4P connector.
7. Turn the ignition switch ON (II).
8. Momentarily connect 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 16.
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 17.
12. Turn the ignition switch OFF.
13. Disconnect the negative cable from the, battery.
14. Disconnect PCM connector A (32P).
15. Check for continuity between body ground and PCM connector terminal A27.
Is there continuity?
YES - Repair short in the wire between the PCM (A27) and the A/C pressure switch.
NO - Substitute a known-good PCM and recheck. If the prescribed voltage is now available, replace the original PCM. If not, check the A/C system for other symptoms.
16. Momentarily connect under-hood fuse/relay box 16P 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 on 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 PCM (A17) and the A/C clutch relay.
NO - Check the A/C system for other symptoms.
17. Measure voltage between PCM connector terminals A27 and B20.
Is there less than 1.0 V?
YES - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM. If not, check the A/C system for other symptoms.
NO - Repair open in the wire between the PCM (A27) and the A/C pressure switch.