Camshaft Position Sensor: Description and Operation

Camshaft Position Sensor:

The Camshaft Position (CMP) sensor is located to the left of the cylinder 2, 4, 6 timing belt cover/exhaust camshaft sprocket. The CMP sensor is a hall effect switching device used to determine the position of the bank 2 exhaust camshaft. The CMP sensor detects a single tooth on the reluctor wheel of the camshaft, which denotes 900 before top dead center cylinder #1 compression stroke. The sensor is used by the ECM to determine when cylinder # 1 is approaching top dead center necessary to synchronize the correct firing order. The CMP sensor is also used to enable sequential or independent fuel injection necessary for lowering tailpipe emissions, improving driveability and to enable spark knock control.

As the reluctor wheel tooth rotates past the sensor, the sensors internal hall effect device pulls the signal circuit to ground. Therefore, the ECM expects to one see one high (5 volts) to low (0 volts) voltage transition once every two crankshaft rotations as the reluctor tooth passes the sensor. The signal circuit should be at 5 volts at all times except when the transition occurs. If an error occurs in the CMP sensor circuit, the ECM will take NO default actions. However, it will attempt to make an good guess on which mating cylinder to provide spark and fuel to based where the engine had stopped on the last ignition cycle. Therefore, if the ECM choose incorrectly, the engine may or may not start on the next ignition cycle. If the CMP sensor signal is lost during the ignition cycle, the ECM will still provide the correct spark and fuel in the appropriate firing order.