Theory Of Operation
WARNING: This page is about a different car, the 2013 RAM 1500. However, it is still accessible from the selected car via links, so may be relevant.
Engine coolant temperature should change at a specific rate from a cold start condition. During a start to run, the output of the engine coolant temperature sensor is compared to an internal reference to verify that the engine temperature rate of change is within its allowable upper and lower limits. The Coolant Temperature Sensor is a variable resistor that functions as a normal two wire 5 volt sensor. The PCM supplies a 5 volt reference and a ground to the sensors low reference signal circuit.