1997 XJ - TCM or TCU??

[djlarroc]

Are these the same part? Is it TCU for 96 and older? 97+?

Have a CEL that gave me code P0743 torque converter clutch solenoid..

Did extensive testing and trans shifts fine, and don't believe it's a solenoid. I bought the solenoid pack, but don't want to install if it's not going to fix the problem.

How can I check to make sure it's the TCM/TCU?

If the CEL is erased, it will come on immediately, once the jeep is shifted into drive.

 

[Tim_MN]

TCM and TCU are often used interchangeably, they mean the same thing. The only way to test a TCU is with an DRB-III scan tool or by installing a known good replacement.

 

[djgrayxj]

Note from DJ
You might have a look at these past post on TCU
Transmission Control Module Location
Info from post TCU location by OP 89CAXJ on April 23-2008
http://www.naxja.org/forum/showthread.php?t=951965
See TCU Pick’s from post #11 by lawsoncl

And TCU location by OP dzrtrataz in http://66.228.124.214/forum/showthread.php?t=912363

It looks like the TCU moved from being attached to the knee kick panel under the glove box to above the foot feed in approximately 1996 or 1997 according to lawsoncl.
----------------
Info on diagnostics from Jeep shifting problem (ITS BAD) by cherokeeproject with 96XJ on Oct 7-2010
http://www.naxja.org/forum/showthread.php?t=1044153
---------------------
Info on diagnostics from AW-4 4wd problems by cherokeeproject with 96XJ on Sept 25-2009
http://www.naxja.org/forum/showthread.php?t=1009623
See post # 2 by joe_peters for diagnostics links

See post # 4 by joe_peters for search tips
My search using tcu naxja brought up about 43,800 results, that’s a lot of info.

Adjusting the kickdown cable link in post # 5 by CaliXJ

 

[O-Gauge Steamer]

Are these the same part? Is it TCU for 96 and older? 97+?

Have a CEL that gave me code P0743 torque converter clutch solenoid..

Did extensive testing and trans shifts fine, and don't believe it's a solenoid. I bought the solenoid pack, but don't want to install if it's not going to fix the problem.

How can I check to make sure it's the TCM/TCU?

If the CEL is erased, it will come on immediately, once the jeep is shifted into drive.

You need to state the year of the Heep. 97 are unique. So, for transmissions and controllers, it is 96 down, 97, and 98 up. An output shaft shaft speed sensor was added in 98. 97s may be the same as the 96 down, I am not 100% sure on that as I do not have a parts list for the pre 97s.

 

[djlarroc]

yes, it is a 97.. built 04/97..

this is the second xj in a row i buy w/eventual tranny problem...

 

[djlarroc]

digrayxj, thanks for those links!

Believe me, i have searched, but i have read over so much crap regarding solenoids and tcu/tcm that i probably missed it.

 

[Ecomike]

Solenoid #3 controls the TC lock up. The brake switch tells the TCU to unlock the TC when the brake is applied, so a stuck brake switch can cause a problem a TC lock up issue. But the 97 ODB-II seems to be telling you that it thinks solenoid #3 is dead (open or shorted?). It could be a wiring problem to solenoid #3, or maybe a fuse fault too, but OBD-II would probably catch that.

 

[djlarroc]

well the way we tested it was, we put the rear on a jack, and a probe into the harness at solenoid 3.

we drove the jeep and the probe would light on and off when the tc would lock and unlock, so we determined it was working correctly, and the cause for the CEL is a bad tcu? the jeep drives normal.. no shuddering, and downshifts appropriately.. suggestions on what else to trouble shoot?

 

[djgrayxj]

Thoughts from DJ, I wood look over this info before you start diagnosing your AW4
Shift Pointers AW4 Diagnostic; By Wayne Colonna look at all 4 pages of his info.
Printed in the October 1997 Transmission Digest
http://www.transonline.com/transdigest/magazines/1997-10/Shift%20Pointers/index.html

 

[kastein]

the solenoid fault testing on the 97s is fairly minimal. All the TCU looks for is an open or a short circuit. If it's setting off the code, you have either a wiring fault or a bad solenoid.

As o-gauge-steamer said, in 98 they added an input speed sensor so the TCU can monitor input (right after the torque converter) and output RPMs, solenoid short/open detection, and use this to figure out if any solenoids are burned out and also if the trans goes into the gear the TCU asked for. I'm not sure, but it may also read engine RPM off the CCD bus and use that to determine the input/output speed ratio of the torque converter to see if it locked up or not. That's on 98 and up only though so it doesn't really apply to you.

 

[djlarroc]

I see.. so even though the tcc appears to be working fine, it could still be a bad solenoid.. I think it told the person who helped me diagnose (naxja member also), that it was stuck on high.. or shorted on high.. something like that.

The jeep takes off fine in D. I had a '98 that had a same problem, but that one would default to 3rd gear so i know what to look for there. i changed the solenoids on that one, but did nothing.. ended up being mechanical at that point. this jeep runs fine, aside from the CEL.