Theory of Operation

WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The Coolant Temperature Sensor is a variable resistor sensor and is used to measure the temperature of the coolant of the engine. The 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 illuminates the MIL lamp after the diagnostic runs and fails once. During this time the customer may experience an engine power derate, and regeneration mode will be disabled. The PCM will turn off the MIL lamp after the diagnostic runs and passes in four consecutive drive cycles.