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Thread: Everything on 42RE Transmission

  1. #1

    Icon928 Everything on 42RE Transmission

    New to the forum so I thought I would post a very good link for anyone having problems with a ZJ's 42RE transmission.

    I had searched around this forum for awhile and haven't seen the link. It is a document on that is 130 pages long, covering pretty much everything you would need to know about the transmission and how to diagnose any problems. I have heard way to many stories of people getting ripped off by a mechanic, saying they need a complete rebuild. It's worth the time to read so you don't have to rely on a mechanic to tell you what's wrong. Read that, and you will be telling them exactly what needs fixed.

    I am currently trying to diagnose fault code 21 given by the transmission control module (TCM), which means there's a fault in the Governor Pressure Solenoid Output. Symptoms being the all too common "limp mode", where the transmission drives in only 3rd gear, unless manually shifted into 2nd (reverse still works). Pretty much just going to run down the checklist in the article until I find the problem. I'm hoping it's just a bad electrical connection somewhere, or just needing to replace the governor solenoid/sensor.
    Until then, waiting for sunrise and a day off work so I can fix this thing. Oh, and if you think that article in the link is worth saving, just click download, sign in with facebook, upload one of your documents to share, and 42RE troubleshooting guide (or you can pay 10 bucks for it if your too lazy to upload something).


  2. #2


    well, limp mode is gone now and the transmission is shifting perfectly. oddly the only thing i did was pull the TCM fuse from the fuse block under the hood. been driving around for several days/hundred miles and no problems. i've heard that disconnecting the battery for several hours is supposed to clear the computer, but pulling fuses to them also works and I didn't have to wait. fault code is no longer showing either. i know this is supposed to be a temporary fix, but since it hasn't started acting up again, it tells me i don't have to drop my pan. most likely a bad connection somewhere. i've also heard that the transmission solenoid is very sensitive to polarity (-/+), which could trip a fault in the TCM if something interupts the ground.

  3. #3
    the logical one fixer5000's Avatar
    Join Date
    Feb 2003


    welcome to ju...nice find. if you hang around long enough youll find just about everything you wanna know here
    99 grand cherokee...mine...gone... now its a 2011 toyota tacoma sport... double cab longbed 4.0

    98 grand cherokee...wifes now a 2016 rav 4 xle
    nothing special just jeeps..... ill hang around to try and help the newbies if possible since i dont fit the toyota fanboy thing.


    automation is the future of manufacturing in the USA... if youre a box packer youre screwed. get educated now

    my jeeps gone. two engines with broken piston skirts were just too much to handle. now i got me a toyota lets see how long that lasts

  4. #4


    My 2002 Wj 4.0 was doing the same, now it doesn't shift out of first geat until about 4500RPM or until i get to around 35-40mph.

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