Diagnostic Aids
WARNING: This page is about a different car, the 2001 GMC Safari and 2001 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
If CKP learn procedure cannot be learned, check for a chipped or damaged reluctor wheel, incorrect CKP sensor alignment to reluctor wheel, excessive crankshaft runout, interference in signal circuit to CKP sensor or incorrect ratio of crankshaft to camshaft pulses.
If PCM receives an incorrect crankshaft to camshaft ratio, PCM will not allow scan tool to enable learn procedure.