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 Powertrain Control Module (PCM) provides a 5-Volt supply to the engine Camshaft Position Sensor (CMP) on the sensor supply circuit. The PCM also provides a ground on the sensor return circuit. The Camshaft Position Sensor provides a signal to the PCM on the sensor signal circuit. The CMP Sensor generates a signal to the PCM as the camshaft speed indicator lobe moves past the sensor. The PCM interprets this signal into an engine speed reading and determines engine position. This sensor is used as a backup sensor if the primary Crankshaft Position Sensor Signal is lost. The PCM illuminates the MIL lamp immediately after the diagnostic runs and fails. During the time the customer may experience a hard start/no start condition. The PCM will turn off the MIL lamp after the diagnostic runs and passes in four consecutive drive cycles.