Theory Of Operation

WARNING: This page is about a different car, the 2012 RAM Pickup. 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 sensor and is used to measure the temperature of the coolant of the engine. The Powertrain Control Module (PCM) supplies 5-Volts to the Engine Coolant Temperature Sensor (ECT) Signal circuit. The PCM monitors the change in voltage caused by changes in the resistance of the sensor to determine the coolant temperature. The engine coolant temperature value is used by the PCM for the engine protection system and engine emissions control. The Engine Coolant Temperature Sensor is located near the thermostat housing. This fault becomes active when the PCM detects a coolant temperature higher than a calibrated limit for a calibrated amount of time. The PCM sets the fault after the diagnostic runs and fails once, but will not turn on the MIL Lamp. During this time the customer may experience an engine power derate, and regeneration mode will be disabled. This fault indicates that an overheat condition has occurred.