P1398

Tests 1 - 2:

Tests 3 - 4:

Tests 5 - 8:

SYMPTOM
P1398 - MISFIRE ADAPTIVE NUMERATOR AT LIMIT

WHEN MONITORED
Under closed throttle deceleration; A/C OFF; engine coolant TEMP above 75 deg; longer than 50 seconds after engine start. Speed at which deceleration occurs must be sufficient for given gear range; eg, above 36 mph in 1st gear or above 65 mph in high gear.

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

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