Coolant Temperature Sensor (CTS)

CTS is located in thermostat housing. Variable resistor (thermistor) sensor transmits electrical signal to ECM proportionate to engine temperature. Low coolant temperature produces high resistance while high coolant temperature produces low resistance.

ECM supplies 5-volt signal to CTS and measures input voltage from CTS. ECM is informed of engine coolant temperature by voltage drop or increase. Coolant temperature is used for fuel management, idle air control, spark timing, EGR operation and other engine operating functions.