This may help. See Post #6 in this thread:
* I have an early model 2004 Itasca Horizon DP and my Vehicle Data Computer (VDC, which goes by other names) is located in the last compartment, next to your transmission computer, next to your side radiator. (See picture.)
You an fix this yourself, but I recommend you use a TV repair shop and spend $50 to make sure you do not damage the circuit board when you clean it... and then just reflow the cold solder joints. (More details can be found in the above link.)
* However, if you have a late model 2004 Winnebago DP (or newer) then you will not have a VDC. Instead, you would have MMDC that does the same function, and your MMDC is located under your dash or near your dash. ...But the MMDC is not known to have internal board problems, because the heat an vibrations are much less in your instrument dash area vs. back by the engine.
Attached are two .pdf files with information from the people (Jim & Jim) who helped me solve this air gauge problem; and I attached my .pdf write-up for your review as well.
Good luck with your repair. It's not hard to remove the VDC. Just don't over torque the bolts when you re-install it and follow the other tips. The good news is that you hopefully will not have to spend $1000 at FL with this information!