A/C Signal Circuit Troubleshooting

WARNING: This page is about a different car, the 2009 Acura MDX, 2008 Acura MDX, and 2007 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

Start the engine.
Turn the blower switch on.
Turn the A/C switch on.
Check the A/C CLUTCH in the DATA LIST with the HDS.
Does it indicate ON?

YES - Go to step 5.

NO - Do the A/C pressure switch circuit troubleshooting (see DTC B2979 OR DTC INDICATOR B AND WINDSHIELD DEFROST: AN OPEN IN THE A/C PRESSURE SENSOR CIRCUIT ).
Check the A/C system.
Does the A/C system operate ?

YES - The air conditioning system circuit is OK.

NO - Go to step 6.
Turn the ignition switch to LOCK (0).
Turn the ignition switch to ON (II).
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 (see A/C SYSTEM TEST ).

NO - Go to step 9.
Turn the ignition switch to LOCK (0).
Jump the SCS line with the HDS.
Disconnect PCM connector A (49P).
Turn the ignition switch ON (II).
Momentarily connect PCM connector terminal A13 to body ground with a jumper wire several times.

Fig 1: Identifying PCM Connector Terminal A13 To Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

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

YES - Update the PCM if it does not have the latest software (see PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM (see PCM REPLACEMENT ).

NO - Check for poor connections or loose terminals at the A/C compressor clutch relay and the PCM. If the connections are OK, check the A/C compressor clutch relay (see POWER RELAY TEST ). Then repair open in the wire between the PCM (A13) and the A/C compressor clutch relay and the other A/C systems.