Coolant Temperature Sensor/Switch (For Computer): Description and Operation

Fig. 18 Engine Coolant Temperature Sensor:

PURPOSE
The combination coolant temperature sensor has two elements.
- One element supplies coolant temperature signal to the PCM.
- The other element supplies coolant temperature signal to the instrument panel gauge cluster.

The PCM determines engine coolant temperature from the coolant temperature sensor.

OPERATION
As coolant temperature varies the coolant temperature sensors resistance changes resulting in a different input voltage to the PCM and the instrument panel gauge cluster.

When the engine is cold, the PCM will provide slightly richer air-fuel mixtures and higher idle speeds until normal operating temperatures are reached.

The coolant sensor threads into the rear of the cylinder head, next to the camshaft position sensor (Fig. 10).

New sensors have sealant applied to the threads.

CIRCUIT OPERATION
The engine coolant temperature sensor provides an input to the Powertrain Control Module (PCM) on circuit K2. The sensor also operates the engine cool and temperature gauge in the instrument cluster on circuit G20. Description and Operation

From circuit K2 the engine coolant temperature sensor draws up to 5 Volts from the PCM. The sensor is a variable resistor. As coolant temperature changes, the resistance in the sensor changes causing a change in current draw. The K2 circuit connects to cavity 26 of the PCM connector.

The PCM provides ground for the engine coolant temperature sensor signal (circuit K2) through circuit K4. Circuit K4 connects to cavity 43 of the PCM connector.