Transmission Temperature Sensor/Switch: Description and Operation

OPERATION
The transmission fluid temperature sensor is integrated into the internal harness within the fluid pan. The sensor has a positive temperature coefficient i.e. resistance increases as temperature rises. It should be noted that this component is NOT serviceable, necessitating the renewal of the internal harness should a fault occur.

MONITORING PROCEDURE
Following engine start-up, if the fluid temperature is greater than 20°C and does not increase by 10°C after 180 seconds, a failure judgement is made. A similar judgement is made should the temperature change by more than 5°C in less than 100 milliseconds. The Malfunction Indicator Lamp (MIL) is illuminated if the failure judgement is made on two successive trips. Sensor output is continuously monitored for out of range values. If a sustained high, or low input to the Engine Control Module (ECM) is seen, indicating a harness or connector fault, a failure judgement is made.