Tranny jerked and went into limp mode... Is it toast?

So, I'm on a trip with my Passat wagon, I've driven over 1500 miles in the last few days and I'm just getting close to my air BNB for the night. Driving along at 55 mph on a rural North Carolina road and suddenly I hear a clunk and the torque converter disengages. I was on flat ground and cruising, not accelerating. I noticed right away that the display which shows the current gear was blank. I pulled off and verified I wasn't leaking anything. When I put it in gear, it clunks and goes, but the torque converter doesn't lock.
I sadly don't have my vag-com with me, it's back home in Missouri.
Any suggestions?
Helpful words of wisdom?
Thanks!

Sent from my S60 using Tapatalk

It's hard to tell what's going on without the codes.

Where in NC are you? if you're near me I could recommend a couple of shops that could take a look at it.

Yeah, I'm in Scranton, over near Ocracoke island, so a ways from where you are. There's a guy who has vag-com that I may be able to use tomorrow. I'm kicking myself for not bringing mine.

Sent from my S60 using Tapatalk

Mozambiquer said:

Yeah, I'm in Scranton, over near Ocracoke island, so a ways from where you are. There's a guy who has vag-com that I may be able to use tomorrow. I'm kicking myself for not bringing mine.

Sent from my S60 using Tapatalk

Click to expand...

Yes, a little far from me. Good luck with your car.

So, I picked up a Ford expedition from the auto auction in Raleigh and rented a tow dolly to bring my car home. Last night we made it to Chattanooga Tennessee where we were staying the night. This morning I went to take the car off so I could use the expedition for running around today, and the car went into gear like it was supposed to, and drove fine for a few miles. I decided to take it down the mountain and get some groceries. It did pretty good, much better than the expedition, but it did go back to acting the same way again after a few miles.
I'm kinda bummed that I wasn't able to take the tail of the dragon, like we had been planning to do.

Sent from my S60 using Tapatalk

OBD works, have to start there. No TCM input (or, limp mode) is full line pressure, and direct/reverse drive only. And of course no converter lockup.

oilhammer said:

OBD works, have to start there. No TCM input (or, limp mode) is full line pressure, and direct/reverse drive only. And of course no converter lockup.

Click to expand...

That's kinda what I am thinking it is, I haven't connected vag-com yet, since I haven't made it home yet. I'll keep you updated.

Sent from my S60 using Tapatalk

Update, I connected vag-com, not surprisingly, I found no connection to the TCM. I could not connect.
The ecm has code 18034 powertrain data bus missing message from tcm. Now to pull the carpet.

Sent from my S60 using Tapatalk

Got the carpet pulled, no water in the TCM box, no corrosion either. After work I'm going to check the powers and grounds to the TCM. I'll keep this updated as I know what's going on. Hopefully this will be a fairly simple fix.

Sent from my S60 using Tapatalk

Got to checking the car out, went through VW diagnostic flow charts and most everything checked good, until I hit the data bus wires, pins 85+86 they were at a whopping 110 ohms from a specified 50-70. I disconnected the abs control module and it went down to 53 ohms. I'm thinking this should signify a break in the can bus wire between the TCM and the ecm, since the abs control module and the ecm have the end resistors of 120 ohms each. Disconnecting the abs control module took that 120 ohm resistor out of the circuit, and it should be at 120 now, but it's only half of the specified, which if I'm thinking correctly, should mean a broken wire in the can-bus system?

Sent from my S60 using Tapatalk

As I remember there are 3 grounds(brown) in the harness to the tcm, however there are splices inside the harness which have a habit of rotting. Steel splice, copper wire. They are located about 8-12" from the tcm connector. They ground somewhere near the right kickout. With bad grounds, I don't think you would have communication with the tcm.

thundershorts said:

As I remember there are 3 grounds(brown) in the harness to the tcm, however there are splices inside the harness which have a habit of rotting. Steel splice, copper wire. They are located about 8-12" from the tcm connector. They ground somewhere near the right kickout. With bad grounds, I don't think you would have communication with the tcm.

Click to expand...

I checked those, and they were good. I cleaned them up anyway and put a bit of dielectric grease on them.

Sent from my S60 using Tapatalk

I was messing with it just a little bit ago, I found the tan plug under the passenger side kick panel, and there was a little bit of corrosion, but not very much, I cleaned that up and was able to connect to the TCM, but only for a little bit. I'm planning to do some more over lunch break.

Sent from my S60 using Tapatalk

Well you are on the right track, cutting out the splices and soldering to ensure integrity to the ground circuits, finding the ground studs in that area, cleaning and applying no-alox compound, never use dielectric anything. Di means two, separate, in greek, in this case, dielectric means separate into two electrically.

So in running through the tests, I just found that I have only 2 k-ohms between the can lines and the ground on the TCM. I'm not sure, but does that mean I have a failed TCM? I also have 64 k-ohms between the can wires and the positive input.
I've load tested all the powers and grounds to the TCM, then I've load tested the individual can and k-line wires to the ecm, I don't know what's left to check.

Sent from my S60 using Tapatalk

Update: I decided I wanted to look at the underside of the TCM board to see if anything looked bad, so I removed the rivets and popped it off. I then checked and there was more resistance to the ground terminal. I then reinstalled the TCM and vag-com connected to it. I then took it for a drive and had no problems with it. It looked like maybe it was somehow shorting out the can wire through the aluminum case of the TCM. Maybe I'll get a new one for my car.
I'll update if it keeps working correctly though.

Sent from my S60 using Tapatalk

As you found, grounds have always been a source of problems. I think your tcm is probably ok.

thundershorts said:

As you found, grounds have always been a source of problems. I think your tcm is probably ok.

Click to expand...

No, actually in my case, it's the TCM that's the problem, it's shorted internally. I did clean the grounds, and the ones in the harness I soldered, though they didn't use the steel crimp sleeve on my car, instead the ground splice is resistance welded together. I soldered it anyway just for kicks. But after repairing them, the can was still down. It wasn't until I removed the TCM aluminum case that it started working again.

Sent from my S60 using Tapatalk

thundershorts said:

never use dielectric anything. Di means two, separate, in greek, in this case, dielectric means separate into two electrically.

Click to expand...

Not 100% correct. While that is the meaning of dielectric, that's not how dielectric grease works. In fact I would say it's been misnamed. It's actually one of the most common compounds used to help with connections. We use it extensively with the connections on the semi trucks and trailers we service, since their connecters get exposed to very harsh elements.
I understand it's a controversial topic to some, and I'm not trying to pick a fight. I'm just saying that's what I use, and it works quite well for me.
I also understand how the confusion started with the name.

Sent from my S60 using Tapatalk