Posted the issues I was having with my Jeep about a week ago and didn’t get any feedback. I have a 98 that has a p0700 (transmission control module) and p0740 (torque converter clutch circuit / open) code. I’ve cleared the codes and the check engine light comes back with the same symptoms every time. Either the Jeep shifts into 4th gear early, then the trans shifts back into 3rd and back into 4th as it should, or the torque converter locks, unlocks and locks again. I’m not completely sure which it is, but it causes the 2 codes to be thrown every time it does it. It kind of seems to do it more when running warm. So far I have replaced TPS, cleaned NSS, and adjusted the TV cable. Planning on changing trans fluid and filter and possibly changing the shift solenoids next. Looking for any other suggestions that could fix my problem.

 

Do a drain and refill using Dex/Merc fluid only.

 

Update: Changed shift solenoids, drained and refilled trans with dex/merc and changed trans filter. Still having the same issue

 

its worth unplugging and re-plugging the the 40 pin TCM connector

other thoughts TPS, VSS sensors and wiring

substitute TCM for used unit

 

TPS is new. TCM was my next thing to replace. Where is the VSS located and how do you change it?

 

 

It's almost certainly not the trans computer or the VSS. Most likely it's the t/c solenoid or the wiring to it. Test with an ohm meter before you start blindly replacing parts.

 

Already replaced the solenoid. Would I test the wiring the same way that you would test for a bad solenoid? Not very good with the electrical stuff lol

 

What I don’t understand either is if it was the the solenoid or wiring, why would the torque converter lock up most of the time? It just unlocks for a few seconds when I have the problem. I’m positive this is what causes the CEL, because it immediately comes on when it occurs

 

I would unplug the trans computer, and measure the solenoid resistance at the connector. That would measure the wiring as well as the solenoids. Maybe have someone wiggle the wiring harness as you measure to help find an intermittent break. Inspect the wiring from the trans and up the firewall for damage. There are two connectors on the pass side of the firewall for the transmission and the NSS you can disconnect and clean as well. I don't believe the trans computer would set a "P0740 - open t/c solenoid circuit" if it were unlocking it based on the brake pedal switch or TPS inputs. In my experience, that code really only comes from a bad solenoid or wiring. Very rarely it's a bad trans computer or a mechnical issue, but those are usually consistent and not intermittent like you described.

 

I’ll give that a try next then. Thanks for the input

 

you can easily test the solenoid resistance at one of the 2 plugs that are beside the engine (FSM shows)

my own parts canon methodology is based soley on having the OEM parts on hand, ( so not suited to some) and the limited number of parts that may cause this issue

I personally would still always attempt to diagnose it first

..which requires downloading the FSM from cruiser54 website, peruse the fault finding section, break out the DVM, and brush up on the electrical..an excellent asset and I suggest you download it

 

I’ll look into it. Thanks

 

I took a closer look at the wiring around my TCM and found an orange and white wire that has been spliced together. Do you think this could cause some problems?

 

I'm just gonna throw this out there because I had similar issues and someone on here gave me the solution which was so ridiculously simple. I changed my trans comp, installed new solenoids, did diagnostics out my butthole, and probably a bunch of other stuff that I can't recall right now. I was ready to get the trans rebuilt, but you know what fixed it? Putting in an extra quart of trans fluid, a suggestion by a fellow member. This may or may not be your solution but just wanted to make sure it was in the mix.