I may have found a resolution. Simple, yet FRUSTRATING!
The gauges on 2000 JCG started malfunctioning after I left it sit for 16 days while I was out of town. Briefly disconnecting the negative terminal, and then reconnecting seemed to temporarily re-set the electrical system; i.e. the gauges came back to life, and the dashboard lights would go off. However, after a brief period of normalcy, the problems would reappear.
I took my vehicle to a mechanic that has experience with electrical issues. After 7 FULL DAYS with the car, he found NOTHING. I picked the car up last weekend, and thought I'd try what I thought would ultimately be a waste of time.
It's been mentioned in several online posts, to disconnect the battery for 10 minutes or more, then reconnect. I did so...for approx 1 hour. Had the car now for 4 days, and electrical problems seem GONE! Gauges are normal; no dashboard lights; overhead console works; door locks work. I also checked the diagnostic codes on my vehicle, and the ones that existed previously, were also gone.
Even though my vehicle is 9.5 years old, apparently there are approx 8 computer systems (or processors) in the vehicle that need to be integrated (i.e need to talk to one another). I'm thinking that it's like a router or a home PC...a re-boot solves many issues. In the case of the car, a disconnect of the power supply for 10 + minutes may reset all of the processors.
Seems to have worked in this case. I wish that I would have attempted the resolution before taking it to the mechanic. $$$ down the toilet. Chalk it up to American ingenuity at it's finest.