The tie between the lights on the top of the console and the shifter is in the wiring harnesses. I am having the same issue after water came in from the sunroof being left open. Did you check the shifter harness and the pins on the shifter assembly? You will have to remove the 4 bolts on the shifter (part UCB 500072) to take a look at them as it is at the bottom right of the unit and there is no room to see in there without lifting it up and out. Here is the corrosion on the harness part of mine, the pins on the shifter itself also had green corrosion on them.

Unfortunately, I ended up breaking pin# 8 on mine after trying to use a Qtip on it rather than just contact cleaner.

Before I broke the pin, D was lit up 24/7 even with the key out. No command shift. After I broke the pin, the D only comes on when the lights are on, but it still stays on D at all times (when the lights are on). Still no command shift, so clearly that harness and pin have something to do with the lighting of the PRND LED's.

cmb6s provided me this link to the schematic in another thread.

 

Sounds like the same issue. I was able to pull mine apart with out any breaks. I took 180 grit sand paper to my console pins and used a pin puller to remove the wiring from the harness I even used lithiam contact grease on the connectors as I put them back together but the problem stayed the same.

 

So did you see corrosion there? My issue was the first start after torrential rains and I had left my sunroof cracked. Even though the interior seemed bone dry, water must have got in somewhere and founds it way into that harness.

All the other harnesses looked clean and fine under there.

I am wondering if the circuit board on the shifter goes bad from the corrosion and short-circuiting of the contacts. I have been looking around for a used one as it does not affect my ability to drive it. The cheapest I have seen is $228 for a new one. I was assuming that would be the ultimate fix.

Now I wonder if I had not broken the pin if I would have actually fixed the problem or not??? The other possibility it to just replace the shifter plate piece (the top part with the PRND lights), which is like $65.00.

 

You could probably neutralize the corrosion with some careful work with a brush and electronics cleaner. I would suggest trying to replace the harness if possible, if not, disassemble the whole thing (carefully) clean it, clean the plug, repair the broken ends. There is a good chance if you can't find the harness, wiring, etc. at a salvage yard, you could find the pins at an electronics supplier..

Were any fused blown? I'd guess if the failure was immediate the electronics could have fried. There are plenty of these in salvage years... Just do some searching.