P1398 Misfire Adaptive Numerator at Limit

SYMPTOM
P-1398 MIS-FIRE ADAPTIVE NUMERATOR AT LIMIT

WHEN MONITORED
Under closed deceleration; A/C off; engine coolant temp above 75 degrees F; longer than 50 seconds after engine start. the speed at which the deceleration occurs must be sufficient for the given gear range.

SET CONDITION
When one of the CKP sensor target windows (40 degrees) has more than 2.86% variance from the reference window.

POSSIBLE CAUSES
- CKP sensor visibly defective
- Notches in crankshaft defective
- CKP sensor defective
- CKP sensor not properly installed