A6 TCM (Transmission Control Module)
 

Where is the TCM located? My audi got really wet on the passenger side (front and rear). Is it possible that this would put TCM into "backup mode"? It seems the car only has 3rd gear right now. All gears are lit up on the dash... Any ideas?

Thanks,
-Andy

Sounds like it took a bath...
 

It is under the carpet in front of the front passenger seat, in a black plastic box. Before you pull anything apart, you may want to look at your insurance coverage and see if it is covered via comprehensive or something. Probably almost a grand just for the TCU part at the dealer, or a few hundred if you find it on e bay or junkyard. Plus the carpet problems whatever those are.

You get at the box by removing the passenger kick panel after pulling away the weatherstripping carefully, then pulling up the sill molding from the front edge most of the way back to the B pillar. Then you wedge up the carpeting and foam insulation, reach in underneath, pull up on the plastic box (it is only pushed into two vertical studs, not bolted down), and pull the box out with the thick wiring harness attached. Then you open it and take a few phillips screws out, undo the connector and now you have the likely waterlogged TCU in hand.

I think it's somewhere underneath the front passenger seat, but I've never accessed it...
 

Quite a few things can cause it to go into limp-home mode ("backup mode"). A VAG-COM scan will tell you more if the TCM isn't completely gone.

Under the carpet, in front of the passenger seat...
 

remove kick panel and door sill trim and fold the carpet back

Re: Sounds like it took a bath...
 

Thanks all... that's what I thought. I am trying to dry it out now and we'll see what happens.

Need to remove, dry, and
 

Yes, it is under the front passenger side carpet. With some difficulty, you can remove it from it's plastic box after pulling up the carpet. If it is wet, remove it and dry it out thoroughly, like in the sun or with a hair dryer. Check the fuse supplying it (as I recall, S16), as it is most likely blown, and replace. After the TCM is dry, reinstall, clear the fault codes to get rid of limp-mode (4th gear only), and see if it works. And clean out the leaves from the cowl drain... .
Good luck!

Re: A6 TCM (Transmission Control Module)
 

I have a similar problem but not as bad my display flashes not all the time though sometimes it appears normally and sometimes it flashes, when it flashes however (BACK-UP MODE) I get a rough idle and sometimes the car actually cuts-off, do you all think that the TCM is 100% responsible for this?

Not necessarily, mine was going into limp-home mode when my MAF was going bad...
 

After replacing the MAF, everything is smoother (including shifting), and it no longer goes into limp-home mode. A really bad MAF definitely cause it to idle rough and possibly stall.

Re: Not necessarily, mine was going into limp-home mode when my MAF was going bad...
 

Sorry for not being in tuned with your abbreviations but what does MAF mean?

Mass airflow sensor (AKA air meter, air mass meter, etc)