Hi I have a 94 rodeo v6 A/T 4x4. It acts like it's in limp mode and must be manually shifted but no O/D or power/winter modes. There are no codes or check transmission light. The range/mode sensor has been cleaned several times but no change. I have checked and tested the power/winter buttons and check transmission light assembly in the center of the dash and they work fine on an identically equipted 93 rodeo when swapped. I have a new battery and the alternator output is 14.2 volts running. All fuses in fuse box and relay box are good. It has been hard to find a correct wiring diagram and I need some Ideas. Please help!

Looks like you've checked pretty much everything I would have recommended. Only thing I would add is to check all your grounds. Actually remove the connection and clean it, corrosion can hide.

Also check the fluid for correct level and also make sure it isnt burnt. Dont know if that would cause the same symptoms (I've never owned an automatic).

Hmmm, don't remember the name of the chip, but kind of sounds like when one of the transmission computer chips went out in my '91 Rodeo; don't have that truck anymore, and the paperwork went with it.

But, I remember it could manually be shifted, but acted like it was in limp mode, had no reverse, power/winter modes.

Sorry, wish I could be of more help. I hope in your case it's NOT a transmission computer chip, at the time, mine thankfully was still covered under an extended powertrain warranty, otherwise it would've cost me around $1k or so.

This is NOT common, in fact, my 1st Rodeo was the only one I have ever heard it happening to. So it's very possible it could be something else.

Did you check that alternator under LOAD?? And, check your accessory belts, make sure they're not slipping.

Well I have done some testing. The 4 trans warning lights in the center of the dash all have a common yellow power wire that has 13.7v. All of the lights have an individual ground that goes to the TCM. When the ignition is turned on the check trans light should flash and ground on the other side of the lamp. What is happening is 9v of feedback from the TCM on all light grounds with the key on so no light. I think the TCM is bad but am not sure which computer it is. I have 2 computers under the drivers side kick panel, One has an ac/delco removable chip in it so I think that one is for the trans. I plan on replacing it unless anyone else has ideas all major grounds are good. Again any help appreciated thanks.