Prizm L4-1800cc 1.8L DOHC (1993)
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Coolant Temperature Sensor (CTS)
The Engine Coolant Temperature Sensor (ECT) is a thermistor (a resistor whose resistance changes as a function of temperature) and is mounted in the
coolant stream. The ECT is a two wire sensor with a referance voltage and a ground provided by the PCM. Low coolant temperature produces a high
resistance and high temperatures result in a low resistance.
The PCM supplies a five-volt signal to the sensor through a resistor in the PCM and measures the signal voltage. The voltage will be high when the
engine is cold and low when the engine is hot.
The ECT sensor provides coolant temperature information to the PCM for fuel enrichment, ignition timing, air management , idle speed control and
closed loop fuel control.
A failure in the ECT sensor circuit should set a Diagnostic Trouble Code (DTC) 22.
