The CMP sensor signal, when combined with the CKP sensor signal, enables the PCM to determine exactly which cylinder is on a firing stroke. The PCM can then properly synchronize the ignition system, the fuel injectors, and the knock control. The CMP sensor has a power, ground, and signal circuit. The PCM supplies 12 volts to the sensor. The PCM provides the ground path, or sensor return circuit, from the sensor. The power and ground circuits are also connected to the CKP sensor. If a problem is detected with the CMP circuit, a DTC P0340 will set.
The crankshaft position (CKP) sensor is a 3-wire sensor based on the magneto resistive principle. A magneto resistive sensor uses two magnetic pickups between a permanent magnet. As an element such as a reluctor wheel passes the magnets the resulting change in the magnetic field is used by the sensor electronics to produce a digital output pulse. This system uses two sensors within the same housing for the V6 engine, and two separate sensors for the V8 engine. The PCM supplies each sensor a 12-volt reference, low reference, and a signal circuit. The signal circuit returns a digital ON/OFF pulse 24 times per crankshaft revolution.