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TCM interchangability?

bigalpha

Moderator
Location
Tucson, AZ
I've got a 95 XJ and I can get a working TCM for around $45 from out of a 96 XJ. Will this work fine in my XJ?


What's the interchangability of the TCM in XJs?

Thanks.
 
bigalpha said:
I've got a 95 XJ and I can get a working TCM for around $45 from out of a 96 XJ. Will this work fine in my XJ?


What's the interchangability of the TCM in XJs?

Thanks.

The AW4 encountered no significant mechanical or electrical changes (I don't count the output shaft changing or the speedo drive - those are "external," and have nothing to do with the TCU,) so if the plugs are the same I'd think the TCU will cross over. I've yet to verify this, tho - so take with the appropriate grain of salt.
 
Will do. Of course, I can't tell for sure if my current TCM works or not. I haven't had much time to slap a multimeter to it to make sure that the TCM works or not.

I also haven't tested the TPS either.

I know, I'm a bad person. Just replacing things before I know they're broke.
 
Well, when the shifter is put into 'D' and I step on the gas, the Jeep barely moves, but it revs up.

I can manually shift the gears from 1-2, to 3, to D.

I unplugged the TCM and I could still shift gears manually; which leads me to believe that the solenoids are still fine and that it's an electrical problem.

I was going to slap a multimeter on the TCM and test the wiring according to the "shift pointers". I just havent had the time to scab a multimeter and test all the wiring to see if the TCM is toast.

I got some guidance that it's possible that if the TCM is functioning property, that the TPS could be to blame.
 
bigalpha said:
Well, when the shifter is put into 'D' and I step on the gas, the Jeep barely moves, but it revs up.

I can manually shift the gears from 1-2, to 3, to D.

I unplugged the TCM and I could still shift gears manually; which leads me to believe that the solenoids are still fine and that it's an electrical problem.

I was going to slap a multimeter on the TCM and test the wiring according to the "shift pointers". I just havent had the time to scab a multimeter and test all the wiring to see if the TCM is toast.

I got some guidance that it's possible that if the TCM is functioning property, that the TPS could be to blame.

Easier to check the TPS, but you'll need an analogue ohmmeter to do it reliably.

Connect between two terminals that should vary in resistance (sorry - I can look them up for you if you like, but I can't remember which offhand) and sweep the lever or the throttle. You should get smooth motion without any "hitches" or "jumps" in the needle's travel - if you do, you have a "flat spot" and it can cause all sorts of headaches. Bear in mind you are going to be less concerned with an "absolute value" than with "meter action" on this test.

Solenoids should test out somewhere around 13 ohms if you check coil resistance. These can be checked with digital or analogue.

You can find the AW4 service manual at the Strokers e-group (groups.yahoo.com/group/strokers) and probably at Pirate. It's ATSG - not the FSM - but the ATSG books are reliable as well.
 
Thanks for the tips. As soon as I can grab a multimeter, I will definitely start testing everything. At this point, it seems that a bad TCU would be so easy; since I can swap one in (maybe).

I am not the most electrically minded, so if I say something utterly retarded, you have my permission to laugh. Hopefully, I can get to testing everything this weekend.

I'll try to keep you updated. Feel free to PM me in a few days to see if I tested and forgot to post, or if I didn't get to test anything.
 
bigalpha said:
Thanks for the tips. As soon as I can grab a multimeter, I will definitely start testing everything. At this point, it seems that a bad TCU would be so easy; since I can swap one in (maybe).

I am not the most electrically minded, so if I say something utterly retarded, you have my permission to laugh. Hopefully, I can get to testing everything this weekend.

I'll try to keep you updated. Feel free to PM me in a few days to see if I tested and forgot to post, or if I didn't get to test anything.

No worries - we all had to learn sometime, you know? I'll try to not laugh openly (but I may chuckle.)

I honestly think that primary education doing away with shop classes is going to cause an awful lot of trouble in the next few years - basic stuff that you should learn in school just isn't being taught anymore. Bugger.

I figure if they're going to make you take art and music (and useless stuff like that - "music appreciation" just didn't cover music I appreciated, and I could care less for art...) then you should also be made to take at least some basic Home Ec (cooking and sewing at least) and basic shop (common power tools, basic wood/metal/plastic working, minor electrical repairs - you know, practical stuff...) Now it's Econ and "Business Ethics" - not everyone is going to be an exec, you know...
 
Ah well, I wouldn't blame ya for chuckling openly (or giggling if you prefer).

I agree with you on all counts. When I was in high school, I took a shop class (building materials, not auto shop) and it sure has helped me a helluva lot more than the stupid music classes I took.

I've been thinking about trying to find a local college that offers night classes on auto mechanics/repair so I can learn more the "right" way.

I always hated those 'fluff' classes that they made me take. I sure have learned alot since I learned about the internet and joined forums for whatever car that I owned at the time (escort, subaru, mazda, jeep).
 
Spend that $45 on a meter and check the basic things like power to the TCM first. Heck Harbor freight frequently has their low end meters on sale for $2, and they're not half-bad.

Anyhow, I don't think that a 96 and 95 TCMs are interchangeable. My 95 and 97 FSMs show that the connector changed, and I'm reasonably sure that was in 96 along with the changed to OBDII. switched to OBD-II?
 
Hum. Would the model numbers for the TCMs be the same throughout different model years? I've still got my TCM exposed in the Jeep so I can go and check it out pretty easy.

I suppose I should buy a multimeter regardless. Since I'm trying to get knowledgable on this stuff anyways. Or, I'll just scab one of the 3 we have at work. hehe.

I'm almost ready to buy the TCM just to see if it fits and works. Just for you, 5-90.
 
bigalpha said:
Well, when the shifter is put into 'D' and I step on the gas, the Jeep barely moves, but it revs up.

I can manually shift the gears from 1-2, to 3, to D.

I unplugged the TCM and I could still shift gears manually; which leads me to believe that the solenoids are still fine and that it's an electrical problem.

I was going to slap a multimeter on the TCM and test the wiring according to the "shift pointers". I just havent had the time to scab a multimeter and test all the wiring to see if the TCM is toast.

I got some guidance that it's possible that if the TCM is functioning property, that the TPS could be to blame.

I just read this thread, and from what I see so far, it sounds like you have no power to the TCU. IIRC the 95 TPS on automatics is a single sided TPS, unlike Renix which has a TCU and ECU side. So if the engine runs OK, it's not the TPS! It could be a bad wire between the ECU and the TCU, or a blown fuse to the TCU or bad power wire to the TCU.

Also the Transmision does not use the electric solenoids to shift in 1-2, and 3 positions when shifting manually, it uses a hydraulic internal valve, called the manual shift valve (IIRC) that is tied to the shifter, so that only confirms that the tranny is mechanically sound, it does not confirm anything about good or bad solenoids.

In summary, it sounds like the TCU has no 12 volt power input, and or no ECU / synthetic TPS input to the TCU.
 
Alright. I went and tested the the TCU for power. The D16 pin shows .5V less than battery voltage. Is this a problem, or is there some wiggle room there?

For some reason, lately, the Jeep has been idling very rough and sounds like it wants to die. When driving, it's fine, and after running, it idles fine.

I'm going to try to check the TPS connections at the TCM.

I did run into something that has me stumped: according to http://www.transonline.com/transDigest/magazines/1997-10/Shift Pointers/index.html
the wires are going to be different colors. However, mine don't really match what this guide says. Also, I don't have some wires at some of the pins that this guide says I should have. Any ideas on why that is?
 
There's some wiggle room - you have things like "internal conductor resistance" and "transmission distance loss" to think about, plus the fact that you will always lose .05-.1VDC or so at each "breakable" connection. If it's still over the nominal 12.0VDC, you should be fine.

As far as the wiring colours - it's always possible that the factory that made the harnesses ran out of, say, orange wire and used yellow instead. I've run across that - it's rare, but it happens (and usually calls for an entry into the notebook I keep on that vehicle...)

Check the solenoids - there are three. You should be able to access the feeder signals for them from the harness, and use the chassis for the ground. That's probably the better way to check them anyhow - if any of them test out bad, then drop the pan and check at the solenoid (to isolate whether it's a solenoid fault or a wiring fault) and repair/replace as indicated.
 
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