Engine Temperature Sensor: Description and Operation

Description
The Engine Coolant Temperature (ECT) sensor is a thermistor which controls the signal voltage to the Powertrain Control Module (PCM). The PCM supplies a 5 volt reference and a ground to the ECT sensor. Whenever the engine is cold, the ECT sensor resistance will be high.
As the engine warms up, the ECT sensor resistance decreases and the voltage drops. At normal engine operating temperature, the voltage will be between 1.5 and 2.0 volts.
The engine coolant temperature sensor is one of the inputs used to control:
- The fuel delivery
- The Ignition Control
- The Evaporative Emission (EVAP) canister purge valve
- The Idle Air Control (IAC) valve