94 XJ will not shift itself

And are all tcms interchangeable??

91-95 should be interchangeable. The TCU will have a green connector. A grey connector would be from the earlier Renix, and a red connector would be from a grand cherokee with the chrysler tranny - neither of those will work properly. If you have someone near you, a temporary swap with a known good unit might be very helpful. If your near North Idaho, I have a spare 91 on the shelf I'd give you.

No wire on D1 is normal as the TPS supply voltage comes from the engine computer whereas the Renix setup supplied voltage from the TCU. C14,C15,C16 good as in within the acceptable resistance range, I presume?

With the key on, in park. Do you see voltage on pin C16 (solenoid 1)? To command the shifting, the TCU applies voltage as follows. Note that manually shifting overrides this:

1st Solenoid 1 On, Solenoid 2 Off
2nd Solenoid 1 On, Solenoid 2 On
3rd Solenoid 1 Off, Solenoid 2 On
4th Solenoid 1 Off, Solenoid 2 Off
Solenoid 3 is the t/c lockup.

C16 I checked in ohms like the thing said and was in range.


I'm a little confused with what I'm supposed to do with the solenoid configurations.

CAMO XJ said:

C16 I checked in ohms like the thing said and was in range.


I'm a little confused with what I'm supposed to do with the solenoid configurations.

Click to expand...

I just gave you the solenoid info for reference. The key is that sitting still, you should be seeing voltage applied to C16 from the TCU. In other words, the TCU is trying to command the tranny into 1st gear. If you have power to the TCU, and its not trying to fire up the solenoid that would point to a faulty TCU is bad.

Thanks for the information guys. A guy came by while I was working on and bought it.

did you charge extra for the "manual valve body"??

Hello new member here and my 94 xj is doing the same thing isn't shifting right, I put it into drive and reverse fine bt when we go up the road it doesn't change itself. I've got a 95 xj parts bus that I've been trying to undo the tps to try it in my 94 so I've taken the throttle body off and going to go try that today bt at the moment it idles fine mostly bt it can jump up and down too.

blowen trans control unit fuse, in my case it was a chaffed wire near the firewall, probably done when the head was removed.

i could replace the fuse and all ok start and run a few feet then bam, back to manual shift.

i ran it like that for a couple of years before getting sick of it and getting a "jeep" specialist to sort it out

been running perfect ever since.

so things to look for are first fuses, then if blown ( and from memory it was the one on the inner rh guard, ) and then the wiring loom, especially if you have had head work or done a transfer case drop, as the back of the he'd gets closer to the firewall.

worth a try.

macca