Test J: The A/C Is Always On

PINPOINT TEST J: THE A/C IS ALWAYS ON

J1-J5:

J5-J8:

J8-J9:

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 1424 (TN/BK) then a message 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 3028 (DB/YE). When the PCM energizes the relay, ignition voltage is supplied to the A/C clutch through circuit 1810 (LG/OG). Ground is supplied for the A/C clutch through circuit 1205 (BK).

Possible Causes
- An short to ground on circuit 1424 (TN/BK)
- An short to voltage on circuit 1810 (LG/OG)
- PCM
- EATC module
- EMTC module
- A/C evaporator discharge temperature sensor
- A/C pressure transducer
- A/C control relay
- A/C clutch air gap