DTC P0342: CMP Signal Low: Description

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.

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 1X signal in combination with the Crankshaft Position (CKP) sensor signal in order to determine the CKP and stroke.

The CMP sensor 1X signal is used by the PCM to determine if the cylinder at top dead center (TDC) is on the firing stroke or the exhaust stroke. The PCM can determine TDC for all cylinders by using the CKP sensor signal alone. Observe that as long as the PCM receives the CKP sensor signal, the engine will start without a CMP signal. A slightly longer cranking time may be a symptom of this condition. The system attempts synchronization and looks for an increase in engine speed indicating that the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes that the PCM incorrectly synchronized to the exhaust stroke and re-syncs to the opposite cam position. If the PCM detects that the CMP signal is constantly low, DTC P0342 sets.