DTC P0116: ECT Sensor Performance: Description

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis 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 Engine Control Module (ECM) supplies 5 volts to the signal circuit. When coolant temperatures are low, resistance is high. When coolant temperatures are high the resistance is low. The ECM uses this input for engine controls and enabling criteria for diagnostics. The ECM will record the amount of time the engine is OFF. At restart the ECM will compare the temperature difference between the ECT and Intake Air Temperature (IAT). If the temperature difference is not within the calculated amount, after the predetermined soak time, DTC P0116 sets. Before failing this test, the ECM will check for the presence of a block heater.