Joshcherokee1997

Can i use a TCU from a 97-01 on my 97?
Reasoning is i was going to go to a junkyard and pull one so i could save some money and because not a single auto shop in town carries them.
Thanks for any help.

CobraMarty

What happened to your '97 TCU?

Joshcherokee1997

I have another thread about a transmission issue and they described my issue as my TCU going out or being bad.

https://www.cherokeeforum.com/f2/har...py-rpm-168197/

That Jeep Guy XJMJ

do some questions really need to be answered?

DFlintstone

Radi is pretty sharp on trannys. If he doesn't find you, you might find him. I vaugly remember him, (or someone), mentioning that a bad solonoid (or wire to it?), in the trans can blow the fuse. The plugs and wires to the solenoids are there, rear of the dipstick. You might check that stuff and see if mice or something got in there, or if the wires are rubbing or funky.

Radi

I'm pretty sure 98 and up use an additional trans speed sensor and different speed sensor styles. 96 and older are also different. I've read anecdotal stories of 97-01 TCU's being interchangeable, but I can't verify it, have never personally done it and wouldn't feel comfortable telling you to buy anything but another '97. Perhaps someone who has actually made such a swap will chime in.

Before you go spending money, unplug the TCU and see how it shifts manually. In 1-2 it should hold 1'st gear until you get moving pretty good. 3rd and 4th should follow when you select them (D=4th) That clunk you described in the other thread needs to be ruled out as an internal problem. If it's gone with the TCU unplugged, its' being caused by the solenoids or electronics.
If you still have problems shifting manually there's something in the trans itself, not the electronics or TCU.
See if that fuse holds with the TCU unplugged. If it does, there's a problem with the TCU, wiring or trans solenoids.

The O2 sensor code you describe- voltage too high- see here:
https://www.cherokeeforum.com/f2/o2-...oltage-168247/

Finally, give the trans harness a good inspection, clean the connectors and check the solenoid resistance. You can measure it at the TCU connector. 11-14 ohms or so.

If you cannot find a trans wiring fault, the solenoids check out OK, the trans shifts fine manually and you are *certain* the replacement TPS is good, grab another TCU and try it out.

CobraMarty

The '97 TCU that I have looks like an early-'96 electronics with a late '98-2001 plug end. Sort of a hybrid/crossover.

The '98 TCU pin control is different at the first 3 pins- all the rest are the same.
1-Vt/LG- input speed sensor ground
2-Rd/Bk- input speed sensor signal
3-DB/Bk- output speed sensor ground

Joshcherokee1997

I went to pull and pay and pulled a TCU from another 97 XJ installed it and it is still having the issue i did that yesterday but today when i get off ill try unplugging my TCU and see if i still here a knock. but it seemed to stop having the issue when i blew the 7-8 fuse in my PDC and set the CEL off again and it seems to be running better can these be related?
also the TPS i got was brand new from autozone.

Joshcherokee1997

Radi I ran my jeep without my TCU plugged in and manually shifted and it ran great didnt knock or do any rpm jumps not sure if it blew the fuse because i forgot to replace it before i drove. but even with the new(but used) TCU i installed it had all the same issues. So could it be wiring then?

Radi

Well, you've ruled out a hydraulic or mechanical trans problem and ruled out the TCU, what's left is sensors, solenoids, wiring and connectors.
Are the fuses holding now and the CEL off? Are you saying it shifts better with the fuses blown? Which fuses?

Joshcherokee1997

It does shift better with the fuse blown. but with the TCU unplugged it still blows the 7-8 fuse in the PDC. and what solenoids are you talking about?

CobraMarty

What CEL/codes do you have?

Joshcherokee1997

Im not sure it came up as high voltage to both O2 sensors.

Joshcherokee1997

Radi i put a new fuse in and drove without TCU plugged in and the second turn i took it jerk like it use to then blew the fuse and started to run fine again. I am so confused.

CobraMarty

Maybe that's your problem and not the trans.