87 Cherokee Pioneer AW4 not shifting

Ok,
I had problems with the jeep starting last friday, whata weekend its been since. Started off with the idler pully self destructing... oh thats a easy fixy...

Well got that done.. then the neutral safety/backup lamp switch decided to fully stop rendering use.. Searched around found you can take it apart clean it good reasemble and test.. it works..

Now comes the fun part.

Now that its back on the road, The jeeps got 154k miles its not shifting for anything, it will just ride along in first till you feather the gas and get it to shift to second, Tried messing with the Power/comfort switch on the dash for the transmission but it seems useless..
I had just bought this jeep about 4 months ago now, it had a ignition kill system "aftermarket and remote starter in it."
Removed all of that garbage upon having problems with a no-start.. which ended up being the ICM.

There was a second connector in the line for the brake switch not sure if this was added for the remote start or not. Theres a blue wire with a blak stripe thats cut and spliced and one wire is still not connected. something to do with the brake switch.

Any ideas on that one?

I am rather car savvy, This is my first older jeep in the family, we have had a 93 and a 95XJ in the family with no problems.

So need info about the AW-4 not shifting, and maybe any input about the wiring with brake switch,


I know a buncha guys locally will know me by my pickup truck.. aka Stomper. Its a 89 GMC S15 with 10" of lift and 33's.

Thanks,
Erik aka Tech

Guess maybe I didnt get to the point.

The transmission will shift if you force it by flooring it then letting off.
Is there anything common with these transmissions?
I know they are electric transmissions and seeking what sends the signal.
It just started without warning so I'm finding it odd that this transmission is just dying.

My first guess would go to the TPS...someone correct me if I'm wrong though.

MoparManiac said:

My first guess would go to the TPS...someone correct me if I'm wrong though.

Click to expand...

This would make sence, I pressure washed the engine down after initial breakdown.
It started missing at first but it cleared up.. I just blamed it a fluke due to the cylinders had been loaded with fuel from cranking when the ICM had failed.

Its been a landslide of parts into this thing so I'll try that right away.
Got a friend in NC that has a parts 90 XJ.. Thank god!

Thanks!

The double switch on the brake is also for the transmission, the netural/range selector switch will affect shifting as will the TPS.

thats exactly how my 87 acted and it was tps

This may seem too simple, but did you make sure the fuse for the trans control module is good? The fuse is located next to the module on the lower dash panel between the ash try and the glove box.

You may also want to unplug, replug the trans computer just to make the connection "fresh".

If your TPS is the stock one, replacement is "routine" maintenance. Calibration of the TPS is a real pain, you have to back probe the TPS. If you are lucky and have a friend with the snap-on MT2500 then you can set it with that test set. TPS callibration is VERY important.

Pressure washing the TPS is a great way to kill it and cause shifting problems. One of the wires to the brake switch tells the transmission computer when the brake is presed so it knows to release the torque converter lockup.

I replaced the TPS, but last night i removed everything and the Mass Air Flow Sensor (I think) fell apart after I accidently unscrewed it and the pieces fell out.

I replaced the TPS put everything back together but it will not turn over w/out giving it gas. Then it just stalls out.

I did not have that issue until the MAF sensor fell apart. So Now I think I need to replace that.

Does that sound like a symptom for the MAF?

It will be a long time before I wash down the engine again!

There is no MAS on a jeep, could you be talking about the IAC Idle Air Control motor?

Yes that is it! You're the man! My local auto parts store told me it was a MAF sensor, thats the last time I take their advice!

Anyway, replacing the TPS solved my shifting problem very well, I think the jeep runs even better now!!

Now it's on to the IAC to fix it once and for all.

Thanks fella's your help is greatly appreciated

Thank you VERY much for the diagram. This will help me alot with tracing the wiring that is minorly torn apart under the dash from the previous owner.

Going to be replacing the TPS this week coming.. gotta wait for payday

I used to have a good friend with a snapon diagnostic tool but I havent talked to him lately.. looks like I'll give him a call as well.

Thanks again guys
Erik