Crankshaft Position (CKP) Sensor

This system uses a magnetic CKP sensor, mounted remotely from the EI module, which protrudes into the block just behind the stator. The reluctor is a special wheel cast into the crankshaft with seven slots machined into it, six of which are equally spaced (60 degrees apart). A seventh slot, is spaced 10 degrees from one of the other slots and serves to generate a sync-pulse. As the reluctor rotates as part of the crankshaft, the slots change the magnetic field of the sensor, creating an induced voltage pulse.

Based on the CKP sensor pulses, the EI module sends 7X reference signals to the PCM which is used to indicate crankshaft position and engine speed. The EI module continues to send these reference pulses to the PCM at a rate of seven per 360 degrees for crankshaft rotation. This signal is called the 7X reference because it occurs 7 times per crankshaft revolution. The 7X reference signal is necessary for the PCM to determine when to activate the fuel injectors.

By comparing the time between pulses, the PCM can recognize the pulse representing the seventh slot (sync pulse) which starts the calculation of ignition coil sequencing.