Test I: The A/C Is Inoperative/Does Not Operate Correctly

PINPOINT TEST I: THE A/C DOES NOT OPERATE/DOES NOT OPERATE CORRECTLY

I1-I4:

I5-I8:

I9-I10:

I11-I13:

Normal Operation
Under normal operation, when A/C is requested, a message is sent over the MSCAN bus to the instrument cluster, then from the instrument cluster through the HSCAN bus to the PCM (EATC systems); or a voltage is sent to the instrument cluster through circuit CH434 (GY/YE), then a message is sent from the instrument cluster through the HSCAN bus to the PCM (EMTC systems).

Ignition voltage for the A/C clutch relay switch is provided through circuit SBB25 (RD). When the PCM energizes the relay, ignition voltage is supplied to the A/C clutch through circuit CH401 (VT/WH). Ground is supplied for the A/C clutch through circuit GD121 (BK/YE).

Possible Causes
- Fuse
- An open in circuits CH434 (GY/YE), SBB25 (RD), CH401 (VT/WH) or GD121 (BK/YE)
- An short to voltage on circuit CH434 (GY/YE)
- PCM
- EATC module
- EMTC module
- A/C evaporator discharge temperature sensor
- A/C pressure transducer
- A/C compressor clutch field coil
- A/C control relay
- A/C clutch air gap