Circuit Description

Powertrain Control Module (PCM) uses dual Crankshaft Position (CKP "A" and CKP "B") sensors to determine crankshaft position. Both CKP sensors are located within one housing. PCM supplies an ignition voltage and a ground for each sensor. During engine rotation, a slotted ring, machined into the crankshaft, causes CKP sensors to return a series of on and off pulses to the PCM. The PCM uses these pulses to decode position of crankshaft. The PCM uses 2 basic methods of decoding engine position: angle based and time based (using either CKP "A" or CKP "B" sensor input). During normal operation, the PCM uses the angle based method. In order to operate in this mode, PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate 24X reference and 4X reference signals. Once initial crankshaft position is determined, the PCM continuously monitors both sensors for valid signal inputs. As long as both signal inputs remain, the PCM will continue to use the angle based mode. When either CKP signal is lost, the PCM will compare the 24X reference signal to the Camshaft Position (CMP) sensor signal. If PCM detects a valid CMP signal, and the 24X reference to CMP signal correlation is correct, the PCM determines that CKP sensor "A" is at fault. However, if the 24X reference to CMP correlation is incorrect, the PCM determines that CKP sensor "B" is at fault. If, while in angle-based mode PCM detects an intermittent loss of either CKP signal, DTC P1372.