DTC P0342: CMP Signal Low: Description

WARNING: This page is about a different car, the 2002 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The Camshaft Position (CMP) sensor works in conjunction with a 1 X reluctor wheel on the camshaft. The Powertrain Control Module (PCM) provides a 12 volt reference to the CMP sensor as well as a low reference and a signal circuit. The CMP sensor determines whether a cylinder is on a firing stroke or on an exhaust stroke. As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which the PCM reads. The PCM uses this 1 X signal in combination with the CKP sensor 24 X signal in order to determine CKP and stroke. This diagnostic for the CMP sensor checks for a loss of CMP sensor signal. Observe that as long as the PCM receives the CKP sensor 24 X signal, the engine will start. The PCM can determine Top Dead Center (TDC) for all cylinders by using the CKP sensor 24 X signal alone. The CMP sensor 1 X signal is used by the PCM to determine if the cylinder at TDC is on the firing stroke or the exhaust stroke. The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes the PCM incorrectly synchronized to the exhaust stroke and re-syncs to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.