Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection

Fig. 2 ETC Sensor:

Monitoring Procedure
The sensor output is continuously monitored for high and low value. If a sustained high or low engine control module (ECM) input (indicating a harness or connector fault) is seen, the relevant diagnostic trouble code (DTC) is stored.

The sensor output is monitored while the engine is running. If the engine has been running under sufficient load for the engine to reach normal operating temperature and the sensor still reads below 30°C then the range / performance failure judgement is made. The DTC is stored if the failure judgement is made on two successive trips

Relevant Diagnostic Trouble Codes
P0116
P0117
P0118

Fig. 1 ETC Sensor Cross Section:

Structure of ECT Sensor (Fig. 1)
The ECT Sensor measures the engine outlet coolant temperature and inputs the ECM. The sensor is mounted on the "B" bank thermostat housing. The sensor is negative temperature coefficient i.e. resistance increases as temperature rises.