czettlera

Hello

I would like to get some help, because I'm stuck a little with my 96 grand cherokee transmission problem. The problem is common, no shifting, starts in 3. gear, the controller is in failsafe mode. I have checked everything that is usual, changed the pressure solenoid, measured the wires, it's all fine. The measurement results shown that the pressure sensor is ok, but there is absolutely no control signal comming out from the pcm to the pressure solenoid (the voltage on the wire is 13,8V all the time, till it shuts down the transmission relay).
What do you think, can I be sure that the pcm has to be changed, or there is something I missed.
If it has to be changed, do you know a good place to buy a used or re manufactured one? (I live in Hungary so only on line shopping can go)
Ebay I have already looked, so other possibilities would be interesting.
Thanks in advance.

dave1123

First of all, welcome to the Cherokee Forum. IDK the answer, but I'll get you started.

This is an export model, right? What engine and transmission do you have in it. US models are only the 4 liter inline 6 and either the 5.2 or 5.9 V8s. This limits us to the 42re or 46re transmissions. Your '96 is OBD-I so you'll have to get diagnostic codes by the flashing of the CEL light method or a scanner. See if you have any codes set in the computer. This will help figure out the problem.

czettlera

Thanks for the welcome. The car is a US model, with 4.0 L6 and 42RE transmission. The only code I have is P0748 pressure control solenoid A electrical. Because my scanner can only see live data from the engine controller and none from the transmission control, I had to do voltage measurements. As first step I have changed the solenoid itself, but nothing changed. The resistance of the new solenoid is 7 ohm, if I close it by grounding, it takes 2,58A. The pressure sensor at 0psi sends 0,78V signal, at 65psi 3,12V. The TPS sensor I can see with the diagnostic tool to work properly. The only trouble I could measure is the PCM, because on the solenoid control wire, there is no grounding signal at all, only the 13,8V.
The only thing I'm not sure, that I didn't miss any relevant component measured.

czettlera

I have decided to change the PCM unit. Does anybody has a good idea where to find a PCM unit P/N: P56043172, or does anybody has one for sale? Important that it has to be shipped to Europe.

dave1123

Try rockauto.com. They have one for $293 USD plus a $90 core charge.

czettlera

Thanks a lot for the information. I'm going to order it, and hope that it will solve the problem. I'll be back with the result, as soon as it arrives.

czettlera

The PCM finally arrived, I put it in, and it shifts like a champ
Thanks for the help Dave

dave1123

That's me, always here to help. I'll always give you my best ideas about a problem, however, remember they are just guesses.

Check your private messages. I'm going to send you a note.

czettlera

Just an additional question. I tested the shifting (this is the first time since i have the jeep, till now i shifted manually) and the rpm for up shifting seams to be a little high for me. from 1. to 2. 2700rpm, from 2. to 3. 2500rpm. Is it normal, or i have some additional issues?

dave1123

It just may be the throttle valve cable needing adjustment. It's also a common problem. If you have the cable with the "D-shaped" adjusting clip, just depress the clip allowing the cable to release and retract itself. Then open the throttle wide, allowing the cable cover to ratchet itself back out. That's it.

czettlera

Dave you were right, I did the adjustment, it was over tighten, and it really good now. Shifts smooth, on much lower rpms. Thanks again.