Since you tried everything, time to have the pro's look at it. Could be a wiring issue to the instrument cluster having a problem. Electrical issues are hard to diagnose, even tougher over a forum like this.
so what to do
i checked + in the dash wiring the wiring is ok i think
i Test the ORANGE, PINK & LIGHT GREEN wires at the Cluster Plug with Key ON there is Voltage on those wires,
i checked all the fuses in the trunk every thing fine
Fuse "CLUSTER", Fuse "RLY IGN1", & Fuse IG-O-BODY"
Looking for a Used DeVille in your area?
CarGurus has 1,983 nationwide DeVille listings starting at $1,600.
Search Cadillac DeVille Questions
Cadillac DeVille Experts