1988 4.0L Auto Cherokee not shifting...
 

Heres a little backstory, this jeep hasn't shifted automatically since day one, we've had it about 3 or 4 years and we have just always shifted it manually to drive it. If you start out in D it starts out in really high gear, but if you shift manually it goes through all the gears really smoothly and once in D it stays in the right gear. Well today I got a wild hair and decided that I was going to try and fix it. So I did a little searching and found out how to check the TPS. With the multimeter connected to pins A and D I get 4.65v, and I read that my output on pins B and D should be 83% of my reference voltage, so 3.85 is should be what I'm shooting for on my output right? Well I adjusted it into spec and took it for a short drive and it still isn't shifting. So I checked the 7.5a trans fuse, and it was blown, so I replaced it with a 10a fuse, still does the same thing. Am I doing something wrong? Am I missing something? It's not a huge deal, but I just want to fix it... If everything is adjusted right and its still not shifting, does that mean my TCM is bad? Any help or advice would be greatly appreciated!

Sounds like it could be bad shift solenoids. They don't go out very often, but when they do they can cause these symptoms. Some of the other guys on here have first hand experience with changing solenoids. Maybe they will chime in.

Also, don't just put a larger amperage fuse in where a smaller one should be. Using a larger fuse could potentially allow too much current to pass through the wiring and burn out or short electrical components.

Well dang :( I was hoping it wasn't the solenoids...Ohh well haha.

I know, I didn't leave the higher amp fuse in there, it was just for testing purposes haha.

Well if it makes you feel any better, I've heard they aren't that hard to replace. How many miles are on the jeep? Also, you should probably adjust your TV linkage (throttle valve linkage).

So, there's a fuse that is inline with the harness that goes to the TCU under the passenger side of the dash. Did you check that one? To me, it sounds like the TCU isn't working. The TPS adjustment won't do anything if the TCU has no power.

^^^
Definitely worth checking into.

I haven't checked that! I'll check it here in a little bit, how hard is it to find? The jeep has 195,xxx miles on it by the way.

Here's some pics of where the TCU is located (not my pic) and the harness which has a resistor and fuse. My fuse was blown when I got my Jeep. The ground wire on the dipstick stud on the engine is very important to the TCU and other sensors. I would recommend cleaning that up really when and re-attaching all the wires there (after cleaning them). Lots of tips on Cruisers sheets too.

Listen to this guy^^^^^^^.

89XJ
 

Try the fuse under the glove box passenger side should be a 10 amp fuse two yellow wires that's what fix mine had the same problem