P1398

Tests 1 - 3:

Tests 4 - 7:

Tests 8 - 10:

SYMPTOM
P1398-MISFIRE ADAPTIVE NUMERATOR AT LIMIT

WHEN MONITORED
Under closed throttle decel with A/C OFF, ECT above 75 °F, and more than 50 seconds after engine start.

SET CONDITION
One of the CKP sensor target windows has more than 2.86% variance from the reference window.

POSSIBLE CAUSES
- Damaged tone wheel/flexplate (crankshaft)
- Sensor connector/wiring
- CKP sensor connector/wiring
- Crankshaft position sensor
- Improperly installed/loose crankshaft position sensor