Computer problem
2000 BMW 528 6 cyl Two Wheel Drive Automatic
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REBUILT HEAD FOR COOLANT IN OIL REPLACED
HEAD GASKET WITH 3MM THICKER .
WHEN ALL WAS DONE ,ENGINE STARTED RIGHT UP
BUT ON SECOND START UP ENGINE LIGHT CAME ON
COMPUTER SHOWED CODE P1397 MY SCANNER SAID
MANF. CONTROL IGNITION SYS OR MISFIRE BUT
ALL ONLINE FOR BMW SAY IT IS CAMSHAFT POSITION SENSOR REPLACED SENSOR ON EXHAUST SIDE AND CLEARED CODE BUT ON SECOND START UP IT CAME BACK SAME CODE HELP PLEASE

How is the intake cam sensor? They fail all the time. There is a production date on it, if OE, replace. Misfire faults can be many things.