P0743 on a 98 XJ with no Driveabililty Problems

1998 Cherokee
4.0
AW4
8.25
Factory 2WD
164k

I have two questions. While driving around today my MIL popped on. I pulled codes and retrieved P0700 and P0743. I know 700 is a generic transmission code and 743 is a torque converter solenoid electrical circuit fault. I have zero driveability problems and my TC still locks and unlocks at about 42mph. The Jeep pulsates a bit when stopping but I attribute that to warped rotors. I assume I need to drop the pan and ohm check the solenoids....most likely replacing all 3. Does this sound right? The MIL popped on once 3 weeks ago and I wasn't able to pull codes....As with today it was nice and hot after about 10 miles of driving.

Second question.....since my XJ is a factory 2wd unit I've been keeping my eye out for a 98-01 parts XJ to do the swap to 4wd. I don't really want to put a dime into a 2wd AW4 but I can't afford to buy or store a parts Jeep right now. This may be stupid to ask, but can I install this upgrade piecemeal? Can I swap in a replacement 4wd AW4 with transfer case and rear driveshaft and run like that for awhile until I get a front axle? Would that cause damage?

Thank you.

Is the Dexron-III/Mercon trans fluid fresh, and full to the line ? Cleaned and adjusted the NSS ? Tested the TPS ?

Yes, you can swap trans/T-Case only, and no it won't hurt anything.

Agreed, in fact that's generally what I recommend when someone blows up a 2wd trans. 4wd ones are easier to find and it puts you one step closer to a 4x4 swap... from there on it's just a d30 and a front driveshaft.

If you can, get the transfer case shift linkage components with the transfer case and transmission.

Since you are getting an electrical fault, there's a chance it's wiring, or it could be the solenoid. Either one can be fixed without replacing the transmission, in fact even if it's a solenoid you can just drop the pan to replace it in-vehicle. Not that I'm trying to convince you not to do a 4wd swap/start one, but the option is there if you're lacking time/money and just want it to be right again.

Thank you for the quick replies.

Tim, The fluid is 2 years old with 5k on it. It does not smell burned and is at the correct level when hot. The NSS was removed and cleaned 4 years ago. I have not tested the TPS. I don't have an O-scope...do I just use my meter and check the output voltage? 0-5V?

Kastein, this sounds like good news. Do you think I can run with the TCC code until I can find a replacement AW4 and transfer case? Rather than spending the money on the solenoids I'd like to put it towards the swap. My XJ has the factory trans cooler and 99% of my driving is in town. Think I'm ok as far as overheating the trans goes? I mean I know its not a great trans but I still need it to get me to work for the next few months.

Yeah, you'll be fine running with the code. All it's saying is that it detected either an open or a short circuit on the wire that drives the torque lockup solenoid. Keep an eye on your temps and if it starts driving funny, look into bumping up the schedule on replacing it.

I would bet you can get the solenoid off a local member for beer money if it comes down to it. Try the NWC classifieds, I bet someone has a junk tranny to pull one out of. Hell, I've given away entire core transmissions with the solenoids and everything else on them simply because I didn't feel like taking the time to haul them to the scrapyard.

A meter (preferably analog - you'll be able to see dead spots more easily that way when the needle freaks out and goes to zero or 5 volts midsweep of the throttle) will test the TPS just fine.

Thank you very much for the info. I'll check out the NWC section and see what I can find.

So there's no difference in the crossmember or TCM as far as the swap goes? It almost seems too easy. I know a 97 won't work because of the single speed sensor.

98NWCherokee said:

Thank you very much for the info. I'll check out the NWC section and see what I can find.

So there's no difference in the crossmember or TCM as far as the swap goes? It almost seems too easy. I know a 97 won't work because of the single speed sensor.

Click to expand...

Don't quote me, as i may not be corret, but here's what i remember.

By the single speed sensor you're referring to the speedo sensor that feeds information to your speedometer, correct?

You should just be able to unscrew it from your current case and screw it into the 97 case.

As for the 4wd light sensor, i'm not sure if the 2wds have the wiring tucked away or if it's not there at all. Either way, you don't need that sensor. You just won't have the lights in the cab to tell you that it's in 4wd.

98NWCherokee said:

Thank you very much for the info. I'll check out the NWC section and see what I can find.

So there's no difference in the crossmember or TCM as far as the swap goes? It almost seems too easy. I know a 97 won't work because of the single speed sensor.

Click to expand...

Correct. Reportedly, you can use a 97 (and only 97) TCU to put a 97 and earlier transmission into a 98 and later. It will involve wiring splicing to get the right connector for the harness to the transmission though. IIRC, a 4x4 transmission from a 98-01 does in fact just plug in. I can't remember if the transfer case indicator light switch wiring is in the same harness (I believe it's in a separate one with the downstream o2 sensor, but don't quote me on that, I haven't checked in quite some time) but the transmission pinout and stuff should just fit. Worst case, you have to run the wires for the transfer case switch.

The crossmember and TCU are most definitely the same 4x4 vs 2x4 for any given year. If you swap to a manual things change significantly, and the trans crossmember is slightly different, but that's another topic entirely.

Kingkong0192 said:

Don't quote me, as i may not be corret, but here's what i remember.

By the single speed sensor you're referring to the speedo sensor that feeds information to your speedometer, correct?

You should just be able to unscrew it from your current case and screw it into the 97 case.

As for the 4wd light sensor, i'm not sure if the 2wds have the wiring tucked away or if it's not there at all. Either way, you don't need that sensor. You just won't have the lights in the cab to tell you that it's in 4wd.

Click to expand...

Nope. I recommend you read the first post of this thread - it covers all the different speed sensors (ISS, OSS, VSS), where they are, what they do, and what years use which ones.

So I'm on the prowl for a replacement AW4 but in the meantime, I'd like to sharpen my skills a bit on the diagnostic side of things. I've spent the last 30 minutes doing quite a bit of searching and I'm just a bit turned around here.....

I'd like to test my TCU/TCM to check for resistance before I consider dropping the pan to do a direct Ohm check on the solenoids. I understand that on my 98 the TCU/TCM is located above the gas pedal on the transmission tunnel in the cabin. Is this correct? How and which pins do I check here for resistance here? Does anyone have a picture? Are the specs for restance the same here as they would be directly at the solenoid? I feel pretty confident if I have to drop the pan and change a solenoid but I don't feel very confident on checking the integrity of the associated wiring. Beyond a visual inspection I'm just a little foggy on definitively determining whether its a wiring problem or a solenoid problem.

Any help would be much appreciated in case I decide to go this route while looking for a replacement trans.

The specs would be exactly the same, the wiring shouldn't have more than a fraction of an ohm of resistance in it.

Pull the plug off the TCU, it's exactly where you think it is. The pins you need to test are:
pin 11 (dark blue/white wire) lockup solenoid
pin 12 (white wire) 1-2 or 3-4 shift solenoid
pin 13 (orange/white wire) (1/2)-(3/4) shift solenoid

Each one should see roughly 11-15 ohms measured to a solid ground point.

Thank you so much kastein.....That really helps me and is exactly what I needed. I'll report back on my findings when I've had a chance to check.

Ok, I must be doing something wrong. I pulled the connector at the TCU and located pins 11, 12 and 13 just as you described kastein (wire colors matched). I inserted a micro connector into each pin cavity and then touched my positive lead to it. I ran my negative lead to a jumper wire and then to the braided ground strap on the firewall. With my auto-ranging meter set to resistance I probed and got a range in milliohms.....between 24 and 5 and generally descending. I tried setting it to just Ohms but it just shows OL. I also tried back probing with a T pin and got generally the same results.

I re-connected the TCU and started the XJ. I ran through all the gears and no problems or MIL.

What am I doing wrong?

Wait, are you measuring the TCU pins or the pins on the wiring harness? You should be measuring the pins on the wiring harness, those go to the solenoids. I'm not sure why you'd be getting those readings.

I'm measuring the pins on the wiring harness, not the module....with the key off.

Maybe the battery is dying in my meter??

Any other thoughts? Am I doing something wrong? Can I hit the harness in the engine bay by the trans dipstick?