I have a 03 4.7 has no bus error in odometer. It starts and runs fine and the no bus goes away when it warms up and drives fine but comes back as soon as it cools off. Also when it says no bus the headlights and all the rear lights, brake lights, blinkers stay on. I replaced the pcm, fuse box and instrument cluster, and cleaned up all grounds I could find. Also I noticed the engine to body ground strap was broke in half I replaced that and still nothing. Any ideas what would cause it to go away when warm? Thanks

 

Look for a loose wire, wire ziptied to parts that heat up, loose connectors, etc. To me it sounds like a connection is only made when something heats up and expands thus pushes a wire or connector in place. While rare a wire could be broken internally but not the cable so check continuity on wires that are used for this area.