Circuit Description

The Engine Coolant Temperature (ECT) Sensor is a thermistor mounted in the engine coolant stream. The Engine Control Module (ECM) applies a voltage (about 5.0 V) through a pull up resistor to the ECT signal circuit. When the engine coolant is cold, the sensor resistance is high signal voltage. As the engine coolant warms, the sensor resistance is less, and the ECT signal voltage measured at the ECM drop. With the fully warmed up engine, the ECT signal voltage should measure about 1.5 - 2.0 V. If the ECM detects the ECT sensor that is stuck within an expected range of movement.