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Trans In limp mode

redsquirrel

NAXJA Forum User
Location
SIN CITY
Ok people I know that tis thread been on here a couple of times so hears the problem, i just need find out what to do step by step. i got a volt meter and lots of time. I just need to know what to look for, wire harrnes under hood and under the dash. So this what a got A 1990 XJ 4x4, Auto trans, 4.0L engine and a atlas 2 speed transfercase, and what is the yellow box under the driver side dash. I dont have a lot of money to spend at throwing parts at the problem and it dose not fix it . My buddy can get a used trans to me for $100 Bucks but no torqe converter, please for give the spelling and thanks for all the help.:roll:
 
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If it IS what you are talking about, that would be the TCU, or trans. control unit. You may want to test/adjust your TPS, which is what most issues involved with the trans are from.
 
The yellow box under the driver side dash is probably the cruise control module. First thing to check is the fuse and holder for the Transmission Control Module. It's a flat fuse holder up under the passenger side dash below the glovebox. It's probably just tucked up there. Remove the fuse and check it. Sometimes there's just corrosion in the holder. Search for TPS adjustment procedure.
 
I do believe that he is most likely looking at the HEGO timer--a non-serviceable plastic box under the driver's side dash of the Renix XJs.

I would like something more than "trans in limp mode" for a problem description before trying to help.
 
Yellow box is indeed the cruise module. I think the emissions timer is at least partially transparent. Neither of those modules have anything to do with the trans.

As said above, what is the problem, it's usually good to know what we're trying to help with.
 
So what *exactly* is the problem (as others have asked)? You haven't said one thing to help us help you.

The yellow box *is* the cruise control module. Don't F with it!
 
The promblem is the transmision dose not shift any gear, I can go only 35 at 4500 rpm . I put it in Drive its seams like it only in one gear, its good for rock crawling but not for the faster trails. :explosion
 
Ok. That's a little more. Is this a trail-only rig?

Anyway, as posted earlier get up under the passenger's side of the dash, locate the TCU, remove the 10 amp in-line fuse in the yellow wire OR unplug the TCU.

Try shifting manually. You should have 1st in 1-2; 3rd in 3; 4th in D; reverse, park and neutral. If you have all of that, then the hydraulic/mechanical aspects of the AW4 are intact. If not, you need a new/used/rebuilt AW4.

If the AW4 shifts manually Ok, then the problem is electrical--the TPS, throttle body pressure cable, the TCU fuse, the TCU, the solenoids in the AW4, possibly the NSS, OR the associated harness for all of those.
 
This is not a trail rig yet once i get a bigger truck the i going to make it a trail rig . I'll start with unpluging the tcu , I'll get back with to let you know it went. Thanks
 
Ok i upluged the tcu , I Try shifting manually. I haved 1st in 1-2; 3rd in 3; 4th in D; reverse, park and neutral. IT shifts manually Ok. So now what to do?
 
Yep. Check for power on the yellow wire to the TCU. If you have power then:

1. Adjust the throttle body pressure cable--quick, free, simple: http://naxja.org/forum/showthread.php?t=1015963

2. Test the TPS to see if it is in spec--if not, adjust it. If you can't get it to adjust properly, replace it and then adjust it.

3. Post back your results.
 
Ok guys thanks for all help, i went down to my transmission guy shop and told him my problem. He the TPS as well, when i go to tell him abiut the rig and what was custom on it. He ask me if the Atlas transfercase had a sdeedo sensor, I said no. So he told me there your promblem there. Put a speedo sensor in trans fix. Well i got to go down to the local junk yard and get speed sensor and wiring harness as old was cut by the old owner, dose any one know what the wiring harness coloring looks like.
 
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Wow, my head really hurts(and you editted that for spelling?).
 
Stop! The speedo sensor in the xfer case does not connect to the trans computer. The tranny has its own output speed sensor near the output on the drivers side that you should check. If you follow the wiring harness on the drivers side of the tranny rearward there should be a wire that goes under the plate that holds the xfer case shift lever. That sensor is a magnetic switch that should close once per revolution, so you can actually check it with a meter if you rotate the output by hand.

Its the round black thing all the way back on the drivers side.
aw4_transmission.jpg
 
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