DTC P0116: Engine Coolant Temperature Sensor Performance: Description

WARNING: This page is about a different car, the 2003 GMC Sierra and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The Engine Coolant Temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The Powertrain Control Module (PCM) supplies 5 volts to the signal circuit and a ground for the ECT low reference circuit. When coolant temperatures are low, 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 the test the PCM will perform a calculation to determine the presence of a block heater. If the temperature difference is not within the calculated amount, after the ignition OFF time, this DTC will set.