Code P012, No 4X Reference Signal From IGN Control Module: Notes

PCM checks for cam pulses being received without 4X reference pulses. If PCM senses no reference pulses, engine will not start because fuel delivery system is triggered by pulses and Code P012 is set.

Engine will start and run after an extended crank with Code P012 set. This is because the 24X reference pulses are being received by PCM. PCM uses this signal for fuel control instead.