Patent ID: 6915767

Claim:
A method of operation for an internal combustion engine having a crankshaft, a camshaft and a positionable phaser for changing a phase angle of the camshaft with respect to the crankshaft, the method comprising the steps of: receiving a series of crankshaft pulses representative of crankshaft rotation, and a series of camshaft pulses representative of camshaft rotation; calculating a base offset cam phase using the crankshaft and camshaft pulses when said phaser is commanded to a reference position; calculating a current cam phase using the crankshaft and camshaft pulses when said phaser is commanded to a position other than said reference position; and determining a position of said phaser based on a deviation of said current cam phase from said base offset cam phase, further including: storing said base offset cam phase at engine shut-down; calculating sample base offset values using the crankshaft and camshaft pulses during a period following engine re-starting, and averaging said sample base offset values; and comparing the stored base offset cam phase to the averaged sample base offset values, and initializing said base offset cam phase based on such comparison.