Alternator and PCM protection What I'm going to describe is a rare event. This is possible with any alternator stock ND or Bosch or even the aftermarket alternators that are bigger amperage output. In a nutshell, at any point, the blue field lead happens to short to ground the entire short is routed back through the PCM. Since the PCM is protected by a shared fuse of 20 amps this means the circuit board fails during these events. There have been two cases of this which is @pepsi71ocean and