A/C Signal Circuit Troubleshooting (R18A)

A/C Signal Circuit Troubleshooting

1.Start the engine, and let it idle.

2.Turn the blower switch on.

3.Turn the A/C switch on.

4.Check the A/C CLUTCH in the DATA LIST with the HDS.

Does it indicate ON?


YES - Go to 5.


NO - Do the A/C system test.n


5.Check the A/C system.

Does the A/C system operate?


YES - The air conditioning system circuit is OK.n


NO - Go to 6.


6.Turn the ignition switch OFF.

7.Turn the ignition switch ON (II).

8.Activate the A/C CLUTCH in the INSPECTION MENU with the HDS.

Is there a clicking noise from the A/C compressor clutch?


YES - Do the A/C system test.n


NO - Go to 9.


9.Turn the ignition switch OFF.

10.Jump the SCS line with the HDS.

11.Disconnect ECM/PCM connector A (44P).

12.Turn the ignition switch ON (II).

13.Momentarily connect ECM/PCM 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/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 - Check for poor connections or loose terminals at the A/C clutch relay and the ECM/PCM. If the connections are OK, check the A/C clutch relay, repair open in the wire between the ECM/PCM (A14) and the A/C clutch relay and the other A/C systems.n