PalmCoastXJ

Hi guys hope y'all can provide me some help here. The jeep is a 91 4.0 4x4 that I picked up a few months ago in good shape. Ok so here is some background; I was driving home one night from work and the trans seemed to be acting a bit weird. It didn't want to shift to the following gear till about 2200-2500 rpm. Then a few miles later what I think was 3rd gear went MIA on me. It seemed like a 5 speed with a shot clutch just free rev with not much movement. So I dropped the gear selector down to 1-2 and it was all still there but still no 3rd. Then a few moments later the CEL came on and 3rd was immediately back. Now with that said the jeep is drivable but still won't shift under about 2100 rpms and once shifted won't downshift. Even if I go wot it won't downshift unless I manually downshift or slow down it will go in the more or less correct gear for the speed. Also if from a stop and I go wot it will shift early like 3500rpms. On top of that when in 4th and give it throttle enough to where normally would have downshifted when letting up of the gas it gives a little buck trans wise as if torque converter is locked when in 4th. As for engine codes, reading that darn light is a challenge in itself and it shows maybe 4 codes but I can only positively say I can decipher 2 which are 15-no speed/distance sensor signal and 24- throttle position circuit out of range. Going to post a video as soon as I can maybe some of you can help me with the codes. The speedometer has been on the fritz since i got it and worked when it wanted to but since has not worked not sure if related or not. Since i had no cel codes prior i'm kind of leaning toward a central source maybe the tcm. Idk thanks for any incite in advance.

PalmCoastXJ

http://i79.photobucket.com/albums/j1...6/ce5ff4db.mp4

Here a link to a video of my cel blinking if you guys can help decipher.

cruiser54

Under the dash on the passenger side under the glovebox is the TCU: Transmission Control Unit. It has a harness with some yellow tape around it. In that harness is an inline fuse for the TCU. That fuse can blow or just become corroded. Very likely your problem. Also verify that the harness is plugged securely into the TCU.

BrofessorXJ

X2 beat me to it. I forgot to plug mine in after working under the dash and it caused my tranny to act real funny.

DFlintstone

xxx^ Yea, mine slips ect with the fuse out.

There is a supper easy button/adjustment for the trans kickdown cable at the throttle body. I just push the button, then slide the deal with the taper on it until there is zero play in the cable. It should not be tight, or loose. I really think you should check that as well.
(There is another procedure that is not for dyslectics.)

The TPS has both a trans side and an engine side. Since you got a code for it and it can be checked with a $5 meter, you might consider that. Best of luck!

mud-dog27

hey look....everyone beat me to what i was going to say......guess its been covered that much in the last week.

To the mods could we PLEASE get a sticky with regards to this transmission issue? Thanks.

< DECENT apparently im a seasoned member now

PalmCoastXJ

I read about the fuse in another thread so yesterday I tore apart the dash and looked at the tcm. There was no inline fuse in yellow tape. The harness coming out of the tcm leaving had a connector on it for diag maybe idk then it runs back to the firewall. I'll take it apart again today and take some pictures so you guys can confirm.

cruiser54

Unplug the TCM, spray out both halves of the connectors and plug it back in. Can't hurt. You absolutely sure there's no inline fuse near the TCU? It would be odd if there isn't.

freegdr

maybe its only on renix models

cruiser54

I think it was still there for a few years after Renix. Maybe even up to 93.

freegdr

wireing diag herehttp://www.jeep4x4center.com/knowledge-base/index.htm

cruiser54

This is interesting. Found it searching for "TCU fuse". I just don't remember if the 91 had a fuse panel under the hood.




Remove the fuse from your power center (under hood) for the transmission control unit. This will cause the trnasmission to act like a manual valve body (it shifts into whatever gear you select - not automatic). Now try the transmission in 1, then 3 (you won't have 2), then OD. Shift at the proper speeds. If the trans shifts properly (not much lag or slippage) then you have an electric control issue. If the shifts are very slow or it slips alot it is mechanical.

freegdr

found thishttp://www.jeepforum.com/forum/f11/tcu-fuse-861610/

cruiser54

Must have gone away with Renix, but possibly one in the PDC under the hood?

PalmCoastXJ

So I did what cruiser54 said and unplugged the trans fuse from the underhood fuse box and shifts manually fine so slippage or anything but wasn't slipping before either. Time to check throttle position sensor? Can anyone look at the vid I posted and see what the other codes where thanks