I have an 05 Expy. I havent seen your problem but I have had a few random check engine lights.
I bought the Silverleaf diagnostics software and cable and put my laptop on the dash.
It let me know that I had a problem with a turbo boost sensor that turned out to be a bad connector at the sensor and I had a low water signal from the coolant tank.
It would tell you if you actually have a problem or if its just the display going wack which would be my guess.
Freightliner wanted $175 just to read the codes, nothing else so I bought the Silver leaf for about the same price; $250 I think and now I have it.
At minimum I would pull the display out and check the connectors and ground.
