Coolant Temperature Sensor (CTS)

The CTS is located in the thermostat housing. It is a variable resistor (thermistor) type sensor, and transmits an electrical signal to the ECM proportionate to engine temperature. Low coolant temperature produces high resistance while high coolant temperature produces low resistance.

The ECM supplies a 5-volt signal to the CTS and measures the voltage that returns. By measuring the voltage drop between the 2 readings, the ECM is informed of engine coolant temperature. Coolant temperature is used for fuel management, idle air control, spark timing, EGR operation, canister purge operation and other engine operating functions.