Engine Coolant Temperature Sensor

The Engine Coolant Temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. An ECT sensor monitors the temperature of the coolant. This input is used by the Powertrain Control Module (PCM) for engine control, and as an enabling criteria for some diagnostics. The PCM supplies 5 volts to the signal circuit. When coolant temperatures are low, the resistance is high. When coolant temperatures are high, the resistance is low. The PCM uses this input for engine controls and enabling criteria for diagnostics. The PCM will record the amount of time the engine is OFF. At restart the PCM will compare the temperature difference between the ECT and Intake Air Temperature (IAT). Before failing this test, the PCM will search for the presence of a block heater. If the temperature difference is not within the calculated amount, after the predetermined soak time, or if engine coolant fails to reach a present target temperature before a calculated air flow is accumulated, a related Diagnostic Trouble Code (DTC) sets.