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 Powertrain Control Module (PCM) provides a 5-Volt supply to the Crankshaft Position Sensor (CKP) on the sensor supply circuit. The PCM also provides a ground on the sensor return circuit. The Crankshaft Position Sensor provides a signal to the PCM on the Crankshaft Position Sensor Signal circuit. The CKP Sensor generates a signal to the PCM as a notch in the crank pulley travels by the sensor. The PCM uses this signal to determine engine speed and engine position. The PCM illuminates the MIL lamp immediately after the diagnostic runs and fails. During this time the Camshaft Position Sensor is used to provide engine speed and position information to the PCM. The customer may experience an engine misfire as control switches from the primary to the backup speed sensor. The PCM will turn off the MIL lamp when the diagnostic runs and passes in four consecutive drive cycles.