Neutral Profile Correction And Non Volatile Memory

Neutral profile learning is used at end of line to learn profile correction through a series of one or more neutral engine RPM throttle snaps. This allows the misfire monitor to be activated at the assembly plant. A scan tool command is required to enable neutral profile correction learning. Learning profile correction factors at high speed (3, 000 RPM) neutral conditions versus during 97 to 64 km/h (60 to 40 MPH) decelerations optimizes correction factors for higher RPMs where they are most needed and eliminates driveline or transmission and road noise effects. This improves signal to noise characteristics which means improved detection capability.

The profile correction factors learned at the assembly plant are stored into non volatile memory. This eliminates the need for specific customer drive cycles. However, misfire profiles may need to be relearned using a scan tool procedure if major engine work is done or a new PCM is installed. Relearning is not required for a reflash.

On selected vehicles, the neutral profile correction strategy is the only method used for profile correction learning. In the event of a loss of non volatile memory content (new PCM installed), the correction factors are lost and must be relearned. The P0315 DTC is set until the misfire profile is relearned using a scan tool procedure.