A/C Signal Circuit Troubleshooting
  1. Start the engine, and let it idle.
  1. Turn the blower switch on.
  1. Turn the A/C switch on.
  1. Check the A/C CLUTCH in the DATA LIST with the HDS.
Does it indicate ON?
YES -
Go to Step 5 .
NO -
  1. Check the A/C system.
Does the A/C system operate?
YES -
The air conditioning system circuit is OK.■
NO -
Go to Step 6 .
  1. Turn the ignition switch OFF.
  1. Turn the ignition switch ON (II).
  1. Activate the A/C CLUTCH in the INSPECTION MENU with the HDS.
Is there a clicking noise from the A/C compressor clutch?
YES -
NO -
Go to Step 9 .
  1. Turn the ignition switch OFF.
  1. Jump the SCS line with the HDS.
  1. Disconnect ECM connector A (44P).
  1. Turn the ignition switch ON (II).
  1. 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 -
Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM. ■
NO -
Check for poor connections or loose terminals at the A/C clutch relay and the ECM. If the connections are OK, check the A/C clutch relay, repair open in the wire between the ECM (A14) and the A/C clutch relay and the other A/C systems.■