DTC P012: No 4X Reference Signal From Ignition Control Module: Description
NOTE:
Vehicle will start and run after an extended crank with Code P012 set. This is because 24X reference pulses are being received by the PCM and the PCM can use this signal for fuel control instead.
The PCM checks for CAM pulses being received without 4X reference pulses. If the PCM senses no reference pulses, the engine will not start because the fuel delivery system is triggered by the reference pulses and Code P012 is set.