Crankshaft Position Sensors

The PCM uses dual crankshaft position (CKP A and CKP B) sensors to determine crankshaft position. The CKP sensors are mounted in the engine block approximately 21.5 degrees apart from each other. Three wires connect each CKP sensor to the PCM. The PCM supplies an ignition voltage and a ground for each CKP sensor. During engine rotation, a slotted ring, machined into the crankshaft, causes the sensors to return a series of ON and OFF pulses to the PCM. The PCM uses these pulses to decode the position of the engine crankshaft.

The PCM uses two basic methods of decoding the 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, the PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate MEDRES (24X reference) and LORES (4X reference) signals. Once the initial crank 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 MEDRES signal to the Camshaft Position (CMP) sensor signal. If the PCM detects a valid CMP signal, and the MEDRES to CMP signal correlation is correct, the PCM determines that CKP sensor A is at fault. However, if the MEDRES to CMP correlation is incorrect, the PCM determines that CKP sensor B is at fault.

If the PCM detects a loss of signal for CKP sensor A, DTC P0335 will set. The PCM will switch from angle based mode to Time Based mode B using CKP sensor B signal input. If the PCM detects a loss of signal for CKP sensor B, DTC P0385 will set. The PCM will switch from angle based mode to Time Based mode A using CKP sensor B signal input. A noisy signal input from either CKP sensor will cause the ignition system to re-sync. If the number of ignition system re-sync is more than a calibrated amount, DTC P1372 will set.