1997 BMW M3 No Crank No Start, then crank no start

This is my neighbor Sam's 1997 BMW M3 he purchased last year. Last week he turned the key and it wouldn't start. But... the starter is fine. So he bypassed the EWS and it cranked, but would not start. And we could not "push" start it either. So... thinking he had an issue with the crank position sensor, we replaced that. And... it's strange... but it runs, but is throwing a crankshaft sensor error, even though he installed an OEM sensor... So we're scratching our heads now. Next step I think is to check power and ground at the sensor and go from there.