Warning - Stop Engine Light

We've recently inherited our deceased father's 2001 Monaco Diplomat (40' Diesel) motorhome. Several times during the process of building up air brake pressure, the Warning - Stop Engine light will turn on. Shutting down and restarting the motorhome will commence building up pressure until fully aired up. If allowed to idle before moving the motorhome, the lights will appear again and the motorhome is in "Limp Home Mode". (30-35 mph). If the motorhome is started and run before the lights turn on, it runs perfectly (until you stop again and have to start the whole procedure over!). I believe my father had this problem before and had all the fuel filters changed out and that was the last I heard of HIM having a problem, but here it is again....Any ideas for us? We need to sell this rig but I want to resolve this problem first!