Sounds like a vdc problem. The vdc is in the rt rear storage bay just behind rear tires. You will find three boxes with wires. The engine ECM, the Alison trans ECM then the vdc. Mine is the most fwd box. Start coach and while DW is watching voltmeter tap on the vdc to see if voltmeter needle moves. If not all your guages are the same and you can switch the connecter with an adjacent guage. The guages are easly removed, just turn the outer trim ring about 1/8 turn and the ring will come off. You will find two small screws holding guage in place. Just remove screws, guages and switch plugs with a known working guage. If the swapped guage works then order a new voltmeter from fl.
If your voltmeter started to work after smacking the vdc then you have a, some poor solder joints in the vdc. Order one of these or if you are good with a soldering iron resolder loose connections.
Dave and Laura & two cats
02 Discovery with Accord toad
retired auto rv tech and teacher, wife rt nurse