P1391 Intermittent Loss of CMP or CKP

NAME OF CODE
Intermittent Loss of CMP or CKP

WHEN MONITORED
Engine running or cranking.

SET CONDITION
When the failure counter reaches 96 for 2 consecutive trips

THEORY OF OPERATION
A failure counter is incremented whenever the correct number of crank signals is not seen between two cam signals. A bad trip is stored when the failure counter reaches 96. Two consecutive bad trips are required to set the fault.

POSSIBLE CAUSES
- Open or shorted 5 volt supply circuit
- Open sensor ground
- Open or shorted signal circuit
- Excessive crankshaft sensor clearance
- Excessive camshaft sensor clearance
- Damaged crankshaft sensor rotating component
- Damaged camshaft sensor rotating component
- Failed sensor
- Failed PCM