I think the old key trick can read the codes. On my BIL's 95 GC his Overdrive Off light would come on, and turning the key to the run position and back off in succession would get the OD Off light to flash a code. (run, off, run, off, run, off, run) His transmission would keep dropping into "limp home mode" and would run in second or third all the time. He kept getting sensor error codes, but then they would go away and everything would work fine again. He ended up selling it off and forgetting about the problem.
2000 WJ Grand Cherokee Limited, 4.7l V8, Quadra-drive
Farming is easy when your plow is a pencil and you are a thousand miles from the cornfield. -Dwight D. Eisenhower
Don't curse the farmer with your mouth full.
Ah, cows. A thousand roast beef sandwiches wrapped in a gorgeous leather coat.