Misfire Adaptive Numerator at Limit
NAME OF CODEMis-Fire Adaptive Numerator at Limit
WHEN MONITORED
Under closed throttle deceleration; A/C off; engine coolant temperature above 75 degrees; longer than 50 seconds after engine start. The speed at which the deceleration occurs must be sufficient for the given gear range; e.g., above 36 mph in first 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.
THEORY 0F OPERATION
Because of the need for increased engine RPM resolution to detect a misfire, machining variation has to be learned. The crankshaft has two 40 degree windows that are 60 degrees apart. The window for cylinders #1 and #4 is the reference window. This window position is checked against the window for cylinders #2 and #3. If the reference window detects a variance, the PCM will learn this variance and make the appropriate PPM adjustment. If the variance exceeds 2.86%, the trouble code will set.
POSSIBLE CAUSES
- Crankshaft position sensor improperly installed
- Crankshaft position sensor failure
- Crankshaft position sensor crankshaft target variation
- Severely worn crankshaft bearings
- Wiring connector
- PCM failure
- Low compression in one or more cylinders