ZJ Codes / Transmission Problem

[f40lm2002]

Hi,
I'm a Newbie and this is my first post, so here goes with my problem.
1994 Grand Cherokee Laredo 4.0L 42RE Automatic, 160,000 miles with two transmission rebuilds (second was under warranty)then failed again.
Vehicle has been sitting for a year and was parked with the tranny in "limp mode", third gear start no overdrive. Charged battery and jump started, fired right up, will drive and can be shifted manually up to third, as mentioned no overdrive.
Have Haynes and Chilton manuals so pulled codes, only get one , number "12" then a "55". So a PCM problem that can mean many things,
please help point me in the right direction, since the battery was low obviously the battery input to the PCM was disconnected, and I did charge the battery with the cables off so I could clean the terminals for a better contact.
Also I can start the engine in Park with my foot off the brake and move the lever into reverse with my foot off the brake so I have a Park / Lock problem also and probably more.
I would appreciate some input and a starting point to get this tranny back
to shifting and then work on the other problems.
I've read a number of posts on overdrive problems pointing to speed sensors, but I don't want to just start replacing parts if the PCM might have to be replaced.
Looking forward to some feedback from the pro's on the forum.
Thanks,
Lou [smilie=bal_thanx.gif]

[AndyZJ]

You can easily tell if its the speed sensor that is not allowing the vehicle into overdrive because the speedometer on the instrument cluster will not work. Also, Jeeps HATE dead/dying/low batteries, so before i decide its the PCM, i'd get a good good good battery in there to be sure that's not the problem. The shift interlock seems to be the problem on shifter allowing you to go from park to R without brake pedal application. Check the dealer for that since i believe that falls under a recall that Jeep had to pay for. I don't think those ever expire if you never got it done.

[f40lm2002]

Thanks for the tips, went right out for a test drive, cold night here in New England, speedometer works fine, 3,000 RPM at 65MPH, manual shifting no overdrive, switch does not light up when pushed, no difference.
Voltmeter reads 14V at idle with headlights and heater running, no drop in voltage on start up, good Energizer battery, voltmeter stays on 14V at all
speeds.
Where should I look next, is the PCM the probable culprit? Do you have to reprogram a pre-1996 PCM, I have looked on ebay, units run around $250.00 plus core with the rebuilder programming in your VIN number.
Are there any other sensors or solenoids that I should be looking at?
Appreciate any information, could the overdrive switch itself go bad, when
I pulled the codes with the ignition on and pushed the O/D button it lit up,
but nothing when driving in gear.
Looking forward to hearing from the forum.
Thanks,
Lou [smilie=bal_thanx.gif]

[jeepinsky]

I have a '93 GC 4x 4.0 in which I just removed and rebuilt the trans. The problem before the rebuild was nearly identical to yours; pulled out in second or third, no od, so I would manually shift to first to pull out. After rebuild, the condition remained the same. I then swapped out the transmission controller from a known good source (another '93GC) and the problem was solved. The trans controller is located inside the driver side foot well above and left of the steering column mounted to the firewall; it has a pink or orange multi-pin connector. The controller is silver-metal colored and can be unbolted from the firewall from under the hood to the right of and below the brake booster, two thirteen millimeter nuts. Pull the washer bottle for easier access.
Hope this helps...
Joe