The car:
2003 A6 Quattro
Automatic
3.0 Engine
~125k miles

The problem and what I've tried so far:
I turned the car on today to drive it over to my garage to change the oil and rotate tires. (I drove the car 2 days ago for a couple hours with no problems.)

I notice that the ESP, ABS, and CEL don't turn off after starting and that the transmission gear display is blank. I try putting it in drive, and I can feel the car jerk, so I'm pretty sure it's in limp mode.

I turn the car off and turn it on again and no changes.

I try scanning with my OBD scanner and get a communications error. I tried VAG-COM, and it also cannot connect.

At this point, I disconnect the battery, leave it for a couple of minutes, and connect it again with the idea that it'll cause everything to "reset" and that maybe I could scan it with either the OBD scanner or VAG-COM.

After starting, the ESP and ABS lights are still on, but the CEL is off. I try scanning again and VAG-COM can't connect, and the OBD scanner gives me a P0600 code (with the CEL off), which is "Serial Comm. Link (Data Bus) Message Missing." I'm not really sure what that means.

I notice, at this point, that if I turn the ignition ON, but don't start the engine, I get a message telling me to depress the clutch to start the engine. I don't know when that started happening. I usually don't look at the dash when starting. (I usually just get in the car, turn the ignition to ON, put the trans in neutral, and start the engine)



From the little bit that I know and from what I've read online, the transmission not showing seems to be a problem with the TCM and the ABS and ESP lights could be a dirty brake pad sensor or a dirty MAF.


Does anybody have any tips for troubleshooting?

I guess I should add that the transmission was acting up a year and a half ago. When the engine was cold and I tried reversing it would go into limp mode. From what I read at the time, the easiest (and cheapest) fix would be to start in neutral and avoid backing up when the engine is cold. Which has worked fine since. It seemed to even "fix" itself, because I could reverse when the engine was cold this year as well. I have no idea if this has anything to do with my current problem, I figure I should mention it just in case.

Any help/ideas would be extremely appreciated.

I'm supposed to be driving down to South Carolina (from Long Island, NY) on Tuesday, but something tells me that's not going to happen...

 

I went to look at the TCM today, and found what I think to be the problem. The floor on the passenger side is soaked with water. That would definitely short out the TCM. A quick search yielded this: https://www.audiforums.com/forum/sho....php?p=1181353.

I couldn't find this recall listed. Does anybody know if it's a real recall and if they (the dealership) will replace the TCM? I'm assuming it's going to be permanently water damaged...