Hello,

EDIT: P0700 and P0740..(P0743 was last summer - in the text below)

XJ 98 sport. 312kmiles. AW4.
I had the P0700 and P0743 pop up a few weeks ago. Jeep will shift out of 1st and 2nd, but won't go in 4th, so I am stuck at about 50mph at 2k rpm. Even shifting out of 1st and 2nd is I think at higher rpm than normal. I clear the code; it works fine for a few miles then the same behavior comes back the codes as well.
So far I replaced the TPS (Mopar) and the lock up solenoid. That didn't do anything.
Last time I had this was last summer; same behavior. But the codes were P0743 and P0748. I had changed the lock up solenoid and that solved the problem.
I disconnected the TCU; I can shift manually starting in 1-2, then in 3, but it doesn't shift when going into D.
I cleaned up all the connectors I can think of but at this point I am at a loss. I do have 2 shift solenoids and will probably replace them as well tomorrow. I am just not sure what the P0743 is exactly and what else to look for. I don't know how to test if the TCU is good.
Could someone help me diagnose further or give me any advice?
Thank you for your help.

Marc

 

There are a few possibilities, but strange as it sounds, dirty transmission fluid can cause this one. I've personally seen it.

What is the history of fluid changes on this transmission?

Here is a link that shows a couple of others that resolved with a fluid change.

http://www.naxja.org/forum/archive/i.../t-971521.html

 

Thank you. Transmission was rebuilt 130k miles ago. Since then I have had a drain/refill, on average probably about every 40k miles, the most recent being 15k miles ago. The past 2 weeks while working on it I kept the fluid and put it back in since it was looking good and didn't smell burned.

 

0743 is the torque converter clutch circuit. You've already changed that solenoid though? How's the wiring and connectors look?
Out of curiosity, have you adjusted the TV cable? How's the NSS working? Although I can't prove it, I suspect later years need a working NSS for overdrive to operate.

 

Yes, I have adjusted the TV cable. I do not have any issue with the NSS, not that I can tell.
I didn't mention also that it does help to shift smoother if I lift the foot of the pedal to shift in lower gears (just like driving a manual) but it doesn't help shifting in the highest gear. I believe I read somewhere that it meant something but forgot what it was...
Do you think the shift solenoids could be bad? I tested them at the connector in the engine bay and they were within specs; I know however that they can fail mechanically especially when hot. I can't see anything wrong with the connectors or wiring. The plastic connectors of solenoids #1 and OD are broken but they are held off tight to the solenoid by a piece of wire I put there, waiting to find replacement connectors. I thought that could be the issue but when I dropped the pan today they were in there tight and not moving at all.

 

I did a drain/refill. No change. I had cleared the code before. It cames back after just a few miles during the test drive. I tested the solenoids at the harness again when the car was warm. The white wire with black stripe (the TCC solenoid I believe) checks at 15.7, the other 2 on the same row at 15.0. Can 15.7 be considered out of specs? Not really easy to inspect all the wiring all the way to the trans...
Like I said, I just replaced this solenoid. But it was online, $100 for the set of 3. A cheapo that is already bad?
Or should there be something that I should check before I surrender? I am wondering if I am better off bying a "good" solenoid on a site like chryslerfactoryparts or give up and have it looked at by a mechanic..
I will clean up the NSS tomorrow but after that I am not really sure which way to go.

 

Your first step with a P07XX code should be to pull the NSS and clean the internals.