Mis-Fire Adaptive Numerator At Limit (OBD II)

Name of Code:
Mis-Fire Adaptive Numerator at Limit

When Monitored:
Under closed throttle deceleration engine coolant temperature above 176°, and more than 80 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:
One of the crankshaft position sensor target windows has more than 2% variance from the reference window.

Theory of Operation:
Because of the need for increased engine RPM resolution to detect a misfire, machining variation has to be learned. The crankshaft position sensor reference window is continually compared with the windows for other cylinders. When a variance in one of the other windows is detected, the powertrain control module will learn this variance and make the appropriate RPM adjustment. If the variance exceeds 2%, the trouble code will set

Possible Causes:
- Crankshaft position sensor improperly installed
- Crankshaft position sensor failure
- Crankshaft position sensor flexplate target variation
- Severely worn crankshaft bearings
- Wiring connector
- Powertrain control module failure
- Low compression in one or more cylinders