IF YOU DISCONNECT THE CONNECTOR FROM THE PCM YOU HAVE NO POWER AND NO SWITCHED GROUND TO THE SOLENOIDS.
BACKPROBE those wires to find out what the pcm is sending and recieving to the solenoids.
1. Check that the solenoids have power going to them.
2. Check that the pcm is grounding the correct solenoid at the correct time.
Why not take it to someone who knows what they are doing? Just sticking those probes into the connector isnt exactly kosher, either. It can screw up the terminal and cause even more problems....
first of all you are wrong. Turn, if you will, to page 8W-31-7 of your 96 XJ factory service manual. Please observe that the grounds for the three solenoids and the output speed sensor do not go through the connector that the TCU plugs into (C132.) In fact since you refer to a PCM I am not sure you actually know what you are talking about with XJs. The only XJs that have a PCM instead of a TCU and an ECU are 2.5L equipped ones, this is a 4.0L / AW4 combo and has separate trans and engine computers.
Please note that the ground for those three solenoids and the output speed sensor is circuit Z1, an 18ga black wire, and that it leads from the connector for the trans harness (C135) via splice S123 to ground G105, located on the left inner fender wall.
Backprobing is a good idea but not necessary here.
What's this "check that the PCM is grounding the correct solenoid" thing you speak of? Are you even passingly familiar with XJ transmission control? The XJ uses positive side switched solenoids, one side of all the solenoids is permanently grounded (as I explained above) and the other side is switched to 12V to activate the solenoid. On 97 and later vehicles this is done using a Sanken SI5154 intelligent fault detecting positive side switch in a TO220-5 package; I'm not too familiar with the 96 and earlier TCU internals but it should be roughly similar, or possibly just a simple PNP positive side switching configuration since the 96 and earlier do not detect solenoid wiring faults automatically. I have one in the yard, I'll pop it open tomorrow and do some basic reverse engineering on it for curiosity sake.
What he was testing for in the picture was for 12v while the pcm was disconnected from the solenoids.
no. No, he wasn't, read the thread. He was checking solenoid resistance to ground, just using the meter incorrectly (DCV instead of ohms, common new DMM user mistake.)
To test resistance for each solenoid, you need to use the pos and neg from the solenoid itself, NOT an external ground.
technically you are correct, but once you check to make sure the grounds are OK, it's a fairly accurate test and will find at least 75 out of 100 bad solenoids.
And to TRUELY test their function, take the solenoid out of the valve body, have one person blow into the opening on the solenoid while another applies a ground and 12v to it. It will click and change from allowing air to pass, to not allowing air to pass.
yes, again, technically correct but generally AW4 solenoids fail electrically and at that point it's best to just replace all three with brand new ones while you are in there.
I would also like to reiterate /supposedly/ only having an issue with overdrive slipping.
nope. Read the thread, he was having issues with 3rd and possibly OD slipping.
A bad solenoid will affect 2 gears, NOT JUST ONE.
correct. Looking at the shift solenoid table for the AW4 it looks like this is probably not a solenoid issue, but it can't hurt to spend a few minutes probing with a multimeter to find out if there is a simple to fix issue before blowing a bunch of cash on a replacement transmission.
After the amount of flat out incorrect info you've used as a basis for your arguments here I am not sure I would trust your diagnosis, cost estimates, or quality of work at your shop. I'd recommend taking it to a shop that is familiar with jeeps, preferably familiar with XJs as they are one of the few jeep models to ever use the AW4/A340, or at the bare minimum, a shop that employs people who spend a few minutes looking at the schematics for the vehicle in question before flying off the handle and telling multiple people with years of experience working on and experimenting with XJ transmission electronics that they are wrong.