Mis-Fire Adaptive Numerator At Limit
CODE NUMBERScan tool BA (186)
General scan tool P1398
MIL 11
CODE NAME
Mis-Fire Adaptive Numerator at Limit
BACKGROUND
- Because of the need for increased engine speed resolution to detect a misfire, machining variation has to be learned. The crankshaft has two 40 degree windows that are 180 degrees apart. The window for cylinders No. 1 and No. 4 is the reference window. This window position is checked against the window for cylinders No. 2 and No. 3. If the reference window detects a variance, the PCM will learn this variance and make the appropriate engine speed adjustment. If the variance exceeds 2.86%, the trouble code will set.
RANGE OF CHECK
- 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 58 km/h (36 mph) in first gear or above 105 km/h (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.
PROBABLE CAUSE
- Crankshaft position sensor improperly installed.
- Crankshaft position sensor failed.
- Crankshaft position sensor crankshaft target variation.
- Severely worn crankshaft bearings.
- Wiring harness and connectors failed.
- PCM failed.
- Low compression in one or more cylinders.
DIAGNOSTIC CHART