Transmission Connector Refreshing


trans plugs

Over near the transmission dipstick tube are 2 rather large connectors. One is black and goes to the NSS and the gray connector goes to the transmission itselfTCU fuse TCU location

. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.

Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.

Additionally, if your Jeep is an ’87 to ’90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse.

Revised 1-31-2016

29 thoughts on “Transmission Connector Refreshing”

  1. I shifted my automatic renix xj manually for several years thinking there was issues with the transmission. That was what previous owner had told me. Over the course of about 3 years when had time I went down my mental list of issues it could be crossing them off the list as completed. I ran across ur list about 3 months ago and found this tip and did it. When I got to the 15 amp fuse I pulled it and realized it was blown and it looked like it was a little black like it got hot. I went and grabbed a new fuse and threw it in there . Down the rd I went and what do u know! The xj shifts as smooth as silk! Automatically as it should. Thanks. This made my year. Just got done with tip 6.

    1. I too JUST pulled the 10 amp fuse for the TCU and at least I can now use my daily driver with 110K miles to get to work on Wednesday! YIPEE! However, after pulling the connectors for the NSS, TPS, etc and cleaning both ends of the connectors and also cleaning the TCU socket and 10 amp fuse….no luck! So…it’s manual shifting until I can get more ideas of how to correct the problem. Thanks so much for this forum, cruiser54 and the help it has provided.You’re a good dude in my book!

  2. My new to me 89 aw4 w np 242 did a transfer case swap and when I looked for tcu and fuse I found the box under glove box but no wires anywhere to plug into it…why would this be?

  3. Cruiser we met a while ago in 2017 I have a 90 Cherokee with an aw4 and it’s stuck in 2nd gear with the tcm plugged in. Once I unplug it I can shift it manually through all gears I have done all your tips and to no avail. I’m looking for a tcm from parts houses and cannot find one do you have a good one you could sell me or maybe another place to look for the problem. Any help would be appreciated

    1. Unplug your Alternator start the vehicle and see if it shifts into 1st.. If it does then the diode in the alternator is bad. Replace alternator and it should be good to go.

  4. Hey Cruiser! First off thanks for doing what you do! Secondly, I’m having an issue with my auto 90 xj. I started having a random high idle after driving so I tried adjusting the TPS with no luck. So I replaced the IAC and TPS and now the high idle is still there (only after it’s been driving and warm) but it also now shifts through the gears very quickly and won’t downshift when I floor it. I’ve actually had 3 different TPS’ on it within the last couple of weeks. I even threw the original IAC and TPS on and it is still giving me problems when it didn’t originally, except for the high idle. I have done steps 1,3,4,5 I’ve started to attempt 6 but all those wires stress me out! I know I’m checking the voltage correctly on the TPS and each TPS seems to adjust correctly. It’ll read just under 5v. I do have about .6-.8 ohms of resistance. I had 2.8 but adding the extra grounds really helped that. What do you suggest? I feel like it has to be the TPS. The two new ones were fairly cheap from rock auto, maybe that’s the problem. Is there a brand you suggest? Again, thank you for all your help!

    1. mystery high idle i fought was the intake and exhaust manifold gasket leaking. bolts loose and gasket broken and missing parts. new gasket solved high idle issue.

      1. Loose intake manifolds was something we fought for years. Renix models in particular. I wonder if they changed the torque spec at the engine factory with the HO…..

  5. I have a 1988 Comanche 4.0 remix manual transmission. The truck had no reverse lights when I bought it, I replaced the switch on the top of the transmission and reconnected the wires and the truck runs like garbage. We thought this might be a coincidence and thinking it may be something else until we unplugged it again and the truck runs fineAny help would be greatly appreciated. Thank you

  6. Cruiser….do you know if a 1987 TCU connector pinout is the same as a 1988? I bought an AW4 override switch and the instructions state it is for 1988-2001. The instructions have a diagram for the 1988. I cannot find a diagram online for a 1987 to compare the two. Any help is greatly appreciated.

  7. I have a 1994 JGCL 4wd. My problem is when I start the Jeep and take off down the road, I have to take off in 2nd. I do not have 1st or overdrive, and I have to shift manually. However, if I stop, put it in reverse, and then shift it all the way down I get 1st gear. Now let me blow your mind. If I drive this way for about 2 miles, come to a stop, turn the Jeep off then back on, I can put it in drive and it shifts perfectly until the next day, after it sits. Please someone tell me what’s wrong.

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