Check you main power cable from the chassis batteries to the firewall at the front. Our '06 Phaeton on a Freightliner chassis, all systems would shut down completely for 2-3 seconds then everything would come back, all while driving down the road. Problem proved to be main power cable @ the firewall, the factory crimped connector wasn't well crimped...only the shrink tubing was holding the harness together. A swift tug separated the cable from the cable connector that stayed on the firewall connection stud. Replaced the connector and we've no problems in almost two years.
