Engine Coolant Temperature Sensor

Fig 6 Engine Coolant Temperature Sensor:

DESCRIPTION
The engine coolant temperature sensor is installed in the intake manifold next to the thermostat housing.

OPERATION
The sensor provides an input voltage to the Jeep/Truck Engine Controller (JTEC) relating coolant temperature. The JTEC uses this input along with inputs from other sensors to determine injector pulse width and ignition timing. As coolant temperature varies, the coolant temperature sensor resistance will change. This change in resistance results in a different input voltage to the JTEC.

When the engine is cold, the JTEC will operate in Open Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached.