TCU?

[91green]

Bought a 4.0 2wd comanche and it only has reverse and first.  Pulled the 10A fuse for Auto Trans under the hood as mention before and it shifts manually.  Put a new 10A fuse in and it reverted to the condition of only one forward gear.... Do I need a Transmission Control Unit?  Pullef mine and took it to NAPA and O'Reilly's and had no luck finding a replacement...

[HOrnbrod]

Not necessarily, but it could possibly be a bad TCU. You're not going to find this part at any auto parts store - junkyard item only. I have a few new and used - what's the p/n on your TCU tag? Assuming you have a 91 it should be 53008383.

[91green]

Yes its a 91, the part numbèr is 53008383.  Built 8/1990...

[HOrnbrod]

There are some on Ebay. W/o the dealer DBR II test set, there 's really only one way to check the AW4 TCU out; replace it with another.

[91green]

Ok

[91green]

What years are capatible, 91-97?  My brother has a 92 xj with the aw4 trans...

[91green]

Pulled the TCU from the 1992 cherokee and the part number is 56026769... should i even try it?

[HOrnbrod]

Yes. Most all of them will interchange. The major differences were the pin-out locations on the connector. You might lose TC lockup IIRC. The 92 be good enough for troubleshooting..

[91green]

So I bought a 1991 cherokee tcu, installed it and no change tried a '92 cherokee tcu also no change.  Thinking it could be the throttle position sensor?  However, it only has one bolt and it has twisted one T20 bit and broken another.... idk

[HOrnbrod]

You have a 91 - have you checked for fault codes? 

 

https://comancheclub.com/topic/28111-reading-obdi-91-and-92-mj-fault-codes/

[91green]

I have not.  I will now.  New TPS no change just first gear.  Put in a "flows it glows" 10A fuse in the auto trans location and it aint glowing lol

[91green]

Just do not see a place under the dash for my OBDII/EOBD code reader?

[Green Mesa XJ]

There is no OBDII in 1991. There is a port in the engine bay a misshapen proprietary plug, obd maybe I forget the correct term. However the key trick should get you any codes the computer has.

Sounds like there’s a issue getting power to the tcu, these tcu are dead simple essentially Toyota designed computers that rarely fail.
If I remember right there is a auto transmission fuse in the engine bay fuse box, might be worth a check


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[91green]

Just adjusted my kickdown cable, no change.  Took out the 10a fuse, still shifts manually.  Frustrating.  There is a red"Maint Required" light that comes on when driving and stuck in 1-2...

[91green]

Ok I will look for the port

[Green Mesa XJ]

That port isn’t going to be much help unless you have a code reader with a old jeep adapter. It’s on the drivers side fender in the engine bay sort of near the washer bottle if I’m remembering it right

Before 1996 manufactures used whatever proprietary system and port to program their vehicles, so every vehicle was different. After 1996 laws required a unified system for at least reading diagnostic codes there’s still a ton of proprietary software in modern cars.
The key trick shown below might help

Did you check the fuse box in the engine bay? It should be a small 15 amp fuse.



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[91green]

I will try the key trick

 

[91green]

could it be my clock spring in my steering column as the column is partially disassembled for some reason, still has the wheel on and the shifter but the plastics are off and the turn signal lever and starts with pliers.  will try and upload pictures....

 

[91green]

Tried the key trick all i got was 12 and 55....

[Green Mesa XJ]

Those codes sound about normal if the battery was removed in the last 50 starts.

 

Um, you have no clock spring, that’s for models with air bags.

Maybe the ignition switch is screwed up and not allowing power to get to the TCU. Not sure how those switches can fail,because ours hasn’t at least not yet although one time it ran with the radio and other accessories stuck off because of the switch, next restart it ran normal and has ever since. I don’t know if the tcu was or was not getting power when the switch failed.

 

If you column is screwed up maybe you should source a used or rebuilt column and replace the whole thing. Only reason I say this is I personally hate trying to rebuild/repair these 1984-94 columns other folks here may have better experiences and understanding of how to rebuild these columns.

 

Other than the ignition switch (not the key cylinder the big switch with all the wires in the column) I would check the fuses in the engine bay for the transmission and check along the way to see if power for the tcu is any where in the tcu tracking it back from where it should start (engine bay fuse box passenger side near radiator reservoir) up to the plugs for the tcu.

 

 

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[91green]

 

[91green]

[91green]

[91green]

[ParadiseMJ]

On the TCU...

Make sure that you get the proper TCU for your harness.  If you're getting it at a yard or on ebay, make sure that the connector color and the plug color are the same.  I swapped a 94 AW4 into an 88.  I used the 94 TCU (green IIRC) It never shifted properly.  When I looked at wiring diagrams and the 88 TCU and the 94 TCU were wired differently (TPS wasn't getting any power).

So, I grabbed a Renix TCU,  the connector and the plug were cream color.  If you have a green plug and a cream connector it'll never work correctly.