2000XJoverland

Hey everyone, I'm new to the forum, trying hard to solve my P0740 headache.

I've been through many threads that were related to this code and I'm still scratching my head. This past weekend, I changed all three solenoids in the transmission and noted improved shifting, and better general transmission performance. Prior to completing this I would put the jeep in reverse and it would hesitate until I applied throttle at which time it would lurch a bit and then be fine. Similarly, it didn't like finding certain gears and seemed to hunt more for the gear it wanted.

With the new solenoids, I feel that drivability is much improved, but the code remains and I do feel the TCC isn't always locking correctly. It's a 2000 4x4 4 door for reference, and a new throttle position sensor was also done fairly recently.

I've read other posts discussing bad connections/fouled terminals all the way to a NSS or brake light issue. Today I dropped the jeep off at what seems to be a reputable transmission shop and they seemed certain it was the TCC itself and recommended a full rebuild to address all transmission concerns. It was quoted at $3300 which just seems too high for me to spend if there is another fix and if the TCC isn't completely shot. I know I could source a used transmission much cheaper and go that route, but I'd like to see what you guys recommend for further troubleshooting. 229K on the ODO and original AW4 as far as I'm aware.

Any and all input is appreciated!

awg

* disconnect the 7 pin plug near the dipstick that is the solenoid plug, check the manual or search the forum to identify the correct pin cavity and wire color for the TC solenoid

* measure between battery negative terminal and TC solenoid cavity, should be ~14 Ohms (same as other solenoids)

* if not, the wiring harness may be bad (like mine)

* if you have ~14 Ohms, stimulate the solenoid with 12V at the cavity, you should (just) be able to hear it click

I would try to rule this out before I let some damm fool tranny shop rebuild it, or even touch it

The TC solenoid can be wired to be manually actuated, some hardcore off roaders do this, details on forum

2000XJoverland

Thanks for the reply! Do you have a product that you recommend cleaning those contacts with while I'm checking them out? I'm guessing any electrical contact cleaner would suffice. If it ends up being the entire harness, what am I looking at repair wise? Do I need to drop the entire transmission?


I think this jeep has seen some water crossings too which I've read may have some effect on the wiring near the transmission. Where should I be looking under the Jeep for wire issues?

Thanks again

Clayzer

I saw your question on my older post. My XJ has been running strong ever since I cleaned out my NSS.

A dirty or miss aligned NSS might be causing your problem. The transmission and the computer cant communicate properly. Bleepin Jeep has a good video on how to remove and service your NSS. Its really easy to tackle, just be super careful to no break the bolt with the + cut into it. If you pry to hard on it, you can break it.

Mine was all patinaed over inside. I cleaned it with some sand paper and put some dielectric grease on the contacts. Once I reinstalled my NSS, it took a few tests drives to get the clock set correctly.
You need to drive it over 45mph to ensure the Overdrive command is called out by the computer. If the computer still cant see the tranny, it will kick out the P0740 code. Erase the code and re clock the NSS and try again.

If your transmission is truly bad, a used one is like $150. Its not all that difficult to remove, its just heavy and dirty. I bought a harbor freight Tranny scissor lift to make things go alot smoother the last time I had to pull my transmission. I use it as a shop chair when Im not pulling transmissions.

Go to this website to get access to your Jeep's Field Service Manual.
https://xjjeeps.com/

2000XJoverland

Thanks for taking the time to reply! I have suspected the NSS from reading through other P0740 threads. Interestingly enough, I decided to take some contact cleaner to the wiring harness in the engine bay today. I noticed some exposed wiring on the harness going directly to the transmission, so I did my best to cover that up. Since then, the CEL is still on on my dash, but I can't get the ODBII reader to pull any codes at all. This is the same scanner that was previously reading the P0740, so not sure what that's about. The harness going to the NSS also has a completely severed purplish wire, I'm assuming that can't be good, so I am trying to investigate that a little more.

I'll look into doing the NSS too.

Thanks again!

Clayzer

Yeah that broken wire is probably causing your issue. The Purple color is violet in the wiring book. Is the wire just Violet or Violet with a white stripe? When dealing with wires, its important to make a note of the strip color. If Im reading the wiring diagram correctly, both Violet and Violet/white strip go to the Transmission control module or TCM. With this wire broken, your trans computer cant see your NSS. You can physically be in gear so you can still drive your XJ, however since the computer cant verify where your gear shifter is, it cant ask for Overdrive which will cause a P0470 code.

You should be able to splice that wire back together but if you have a pick N pull junk yard near you, you might see if you can just pull an intact NSS with harness and the transmission wiring harness off a junk XJ just to have as a back up incase your harness is super shot.