Tests AA

PINPOINT TEST AA: THE ENGINE OVER-TEMPERATURE WARNING INDICATOR IS NEVER/ALWAYS ON

Test AA1-AA3:

Normal Operation
Engine temperature status is transmitted to the powertrain control module (PCM) from the cylinder head temperature sensor through circuit 8-RJ33 (WH/VT). The PCM transmits an over-temperature status to the instrument cluster over the standard corporate protocol (SCP) communication network, circuits 4-EG8 (GY/VT) and 5-EG8 (BU/WH). When engine temperature, as measured at the cylinder head, reaches 121°C (250°F), the PCM enters the first stage of the fail-safe mode and sends a command message to the instrument cluster to turn on the engine over-temperature warning indicator. Instrument cluster DTC U1073 will be set if the instrument cluster fails to receive the engine temperature status from the PCM.

Possible Causes
- circuit 8-RJ33 (WH/VT) open, short to power or short to ground
- cylinder head temperature sender
- PCM
- instrument cluster