Crankshaft Activity Counter

This signal is called a 7X reference signal. It is because a pulse occurs every 7 times per crankshaft revolution.The PCM uses this signal from the electronic Ignition Control Module (ICM) to calculate engine RPM. A scan tool has two displays based on this input. One indicates crank RPM or simply that the PCM is receiving the 7X reference pulses while cranking. The other indicates engine RPM while the engine is running. If the PCM receives an intermittent signal from the CKP, then the CKP resync counter will increment. More information about this signal may be found in Electronic Ignition (EI) System Description.