I had a similar problem with my 2005 Freightliner Chassis diesel pusher.
My dial gauges always worked but the 16 or so dashboard warning lights would flash continuously and the on board computer display panel would malfunction. The service technicians couldn't figure out what was causing the problem. They even replaced the warning light display module. I eventually discovered that the problem only occurred when I did not fully depress the brake pedal when starting the engine, or when there was low air pressure in the air brake system when I started the engine. If I start the engine after the air has been dumped all the waring lights will cycle and flash again. Once the air pressure has been fully restored, I turn off the engine and then restart it with the brake pedal fully depressed and everything works properly.
