The solution was the crankshaft sensor!

I searched this forum extensively and found similar issues but never a solution. Took over a month starting at the mechanic then towed to dealer. Car would crank but wouldn't start. Multiple codes including DTC P1582 which only can be cleared by dealer per technical bulletin XT303-01.

Cleared codes, checked fuel pressure which was good, Performed immobilization and replacement of ECM, found vehicle to start but die after several minutes, would crank but not start intermittently. Installed fuel gage on fuel rail to read fuel pressure when vehicle would not start - good fuel pressure. Coil and Spark Plug good. Started checking wiring. Vehicle would work one day, fail the next.

Finally, replaced crank sensor - problem solved!