2003 Jeep Grand Cherokee P0123

I have a 2003 Jeep Grand Cherokee, 4.0 liter, with 100,000 miles. I am getting a P0123 (TPS voltage high) trouble code. When the fault is present the transmission acts goofy, and never has the same symptom twice. Once it felt like it was slipping on takeoff from a stop, would shift to second and feel ok. Another time it felt as the trans would not shift into overdrive. I have been told that the reference voltage from the TPS then goes to the trans controll module. Yesterday the trans was acting up so I stoped to check the fluid level and it was ok. The idle started to fluctuate excessivly and when I got back in the car the ses light was on. Once in a while I feel a miss but when that happens I run some injector cleaner through and it clears up. I dont feel that is related to my current problem. Everything else seems to work fine. I welcome any input and thank you in advance.
Have you done anything to test your TPS circuit. The trans takes data from the TPS so you need to resolve that first.
 

I have not done any hands on work other than pull the code and read up on it. It is now 1030 pm and likely will not do anything else tonight. I agree fixing the TPS is a first priority, that is why I am not panicking about the trans. My wife is freaking out however.

Just an update. Since my orrigional posting, the Jeep has not acted up, so troubleshooting has stopped. Just looking for other peoples experiences with the P0123.