Engine Coolant Temperature Sensor

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 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 temperature of engine coolant. ECT sensor is located on top front of cylinder head, near oil filler tube. See Fig 1 . The ECM supplies 5 volts to the signal circuit. When coolant temperatures are low, resistance is high. When coolant temperatures are high, resistance is low. ECM uses this input for engine controls and enabling criteria for diagnostics. ECM will record the amount of time the engine is off. At restart, ECM will compare the temperature difference between the ECT and Intake Air Temperature (IAT). If temperature difference is not within the calculated amount after the predetermined soak time, a DTC will set. To diagnose, see SELF-DIAGNOSTICS - 6.6L SIERRA & SILVERADO - DIESEL article.

Fig 1: Locating Engine Coolant Temperature Sensor

Courtesy of GENERAL MOTORS CORP.