swoop is right, also, in my experience, these codes are what sometimes get set when you have a loose alternator belt or intermittent wire connection at the alternator. (like a loose large wire that is connected by a nut, when the nut is only finger tight), or when someone tries to jump another truck with the jumper cable wrong,
Is this truck an "LPS" rated truck? if so, you may have a problem with the connection internal to the 'LPS' shut off switch that is a cable pulled switch or just someone that pulls the cable to see what it does.
hth