Kohler 20 EORD Diesel Generator

Seems the fault is definitely in the electronics controlling the voltage. A complete redesign of that circuitry may be required. It is not feasible to diagnose the faulty code and circuitry on this forum or in your truck. Do the smart thing and get another supplier or substitute another voltage regulator system.

A brief story. For several years Ford Motor Corp made 'millions' of 'Dura-Spark III' electronic ignition modules for their cars. They all had a random and infrequent 'error' that would cause 'no-spark' sometimes, left overnite they would 'fix themselves' . My spouse had a 1982 Lincoln Town Car that was so affliceted about twice a year -during the entire 5 year warranty period is was picked up 'no-start' and always worked when dropped at the Dealer service facility. After the warranty period, they wanted to start changing all the ignition related parts at several hundred dollars a pop to try and resolve the still randomly occurring condition. We traded the car in on a reliably starting used Cadillac. A couple of years later I was in Caracas in the garage of the national theater when I saw a fellow motorist with the same model as our former car--hood up. I stopped to try and help. He asked me to watch the disconnected fuel line -gas gushed out -faulty fuel gauge made out of gas a possibility). I suggested we they check the spark-- we found -no-spark. His face smiled, he disconnected the battery cables and touched them backwards for an instant. I was shocked and asked why? He said it was well known in Venezuella the ignition module computer would lock up occasionally and the only way to re-boot it was what he did. It worked!