Update
After 3 days chasing circuits with a digital multimeter, cleaning and tightening connections, I finally found where the Allison (and Alladin) gets its 12 volt power. As Eric pointed out there are 2 fuses in the battery compartment that power the engine computers. On my 2006 Monterey there is a third standard blade 20 amp fuse. All three of these are mounted in a small rectangular box with plastic weather covers over the fuses (left wall of the battery box). I chased the source to these fuses back around and into the electrical box where the Big Boy is installed. There is a 35 amp ANL fuse bolted to the chassis battery bus. The other end of the ANL fuse has a ring connector crimped to an 8 gauge wire that runs to that fuse box. As I reached behind the Big Boy solenoid to check the connections, the wire came out of the crimp into my hand. That improper crimp was done at the factory and has been a disaster waiting to happen for 16 years. Evidently, opening and closing the battery tray last week while I worked to install a new injector wiggled that loose connection just enough that every time thereafter when I hit a bump, power was lost to the Allison VIM/ECU. As a side benefit for me, my Alladin now stays powered correctly. For the 5 years that I have owned this coach, my Alladin display would come and go. I thought I had a failing control board on the Alladin, but I now realize that the problem all along was that bad connection to the battery bus. I drove it 4 hours today, no problems. I thank all of you for your assistance. This forum is an invaluable resource.
Richard