Engine - Coolant Temperature Sensor/Switch: Description and Operation

PURPOSE
The coolant temperature sensor (B11/3) measures engine coolant temperature. The information provided by the coolant temperature sensor is used by the HFM-SFI control module to calculate air/fuel mixture and idle speed correction.

Fig. 39 Coolant Temperature Sensor:

OPERATION
Actually there are two independent temperature sensors combined in one housing. Both sensors are the negative temperature coefficient (NTC) type (resistance decreases as coolant temperature increases). The sensor has two ground connections, engine ground and HFM-SFI control module ground. Since both circuits of the sensor have the same resistance curves, the sensor connector can be installed in either orientation without affecting the operation of the circuit.