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Audi A6 Transmission board - water damaged

I have a 99 A6 Quatro - There was a leak in my car while it was stored. The transmission computer board is under the pass seat floor, it was water damaged and I'm told that I also need to rewire the whole connection. Any idea if the rewiring is necessary or is there a better way to connect a replacement board?

Has anyone else had water leakage into this panel?


  • Greetings Toadhollow,
    Before I start typing pages of info, has your Transmission problems been solved to your satisfaction?
    JKAudiA6 :shades:
  • JKAudiA6,
    No, it has not been solved. I'm at a standstill because I'm told that all the wiring has to be redone (not sure that's correct). I was wondering if I connect a new transmission board; should the harness that was also in the water, work????????
    Thanks for responding.

  • Happy New Year, Toadhollow:
    You can answer this one question afterward,but let me say this first.
    Who told you the wire harness had to be replaced and what is the reasoning behind such a statement? Second how did you determine the control unit is defective?
    a. A wire harness under the passenger seat is not a bunch of wires just laying there. They are insulated individually and as a group correct?
    b. If the control board for your transmission was in water for say several months then corrosion of some kind from minerals in the water would have an effect.
    Was it surface water or completely submerged?
    c. While your trying to figure out if replacement of parts, Control boards and wiring
    are needed, I'd be more concerned about how the water got under the passenger seat and fix that first.
    Note: When you don't like or are not sure if the answer you're getting is correct get a second opinion. That's what you do when go to the doctor for health issues and it's not any different for Automobiles. :sick:
    1. The Water problem:
    Check your door seals.
    Check the Drain plugs on chassis under the floor from the outside;ie, Jack the car up and do a visual, if they are rusted or open they need to be replaced.
    Look for water entry points where the door panels butt against the metal door frame.Perhaps the plastic seal between the door panel and metal door frame is broken.
    Check your windows seals where the glass enters the door when opening & closing.
    Find out where the drain point for water is if you have a sunroof it may be stopped up with leafs, or other stuff.
    2. The Transmission Control unit was mounted inside an enclosed box, Yes?
    If you still have the old one, remove it from the box and let it air dry.
    Inspect it for broken solder joints and clean it with a soft bristled brush not cleaning fluids. While it's air drying go to the internet and find an electronic repair Technician
    that specializes in Automotive electronics, preferable Audi Stuff.
    Have them test the control unit and replacement of parts, after you get an estimate of course. This is generally fare less expensive than a new part. Or go to a junk yard and buy one from a wrecked Audi A6 and ask them if you can bring it back should it not work.
    Are you sure the transmission control unit is bad? and was it the guy that told you
    to replace the wire harness too?
    I hope you see what I'm trying to do here.
    One last option: If you go to Audi for a replacement part ask them if they have an exchange program for that part. In plain English this means you buy a rebuild control unit at a reduced price for your old one which they or someone else repairs.
    Have you tried an auto Parts store?

    Let me know how this go:
    Good Luck
    JKAudiA6 :shades:
  • :sick: Hello I have a Audi A6 that has leaked inside after a good rain. Under the passenger seat on the back floor passenger side and front floor passenger side. Now just the other day my transmission went in to limp mode and I was told by a technician that ran a dianostic on my car that the comp. said it had a wirring grounding problem of some sort and it would be $90 and hour in labor to pin point the issue to find the problem. What advice do you have for me concerning this issue.
  • Hi Peatti,
    1. If you went to an Audi dealer and he/she told you $90/Hr. I'd wonder if
    they really had any training from Audi. To put it another way either they know where the ground wires are located or they don't.
    2. The water can come from many different places, here are just a few.
    a. Windshield & or rear window seal not sealed properly.
    Door alignment Rt./side, window & door seals.
    Removing the rear seat lower portion may reveal moisture draining from the rear window down to the foot well area.
    b. Drain system in front of the windshield under the engine hood.
    c. The (B Post) if you have a four door, between the front and rear door.
    d. Pull the Seal belt out on the passenger side, the part that goes in the (B piller) should be dry.
    e. Sunroof drain holes blocked, roll the sunroof all the way back check for leafs or other stuff. Try to determine if the water is Rain water or does it have color indicating Oil or Anti-Freeze content.
    As for the transmission ECU(Electric Control Unit) you should get a copy of the Error report which that technician performed especially if you paid for it. If it was done using the "VAG/VAS" VCDS Diagnostic program it has critical information regarding
    the parts, location and error codes relevant to your Transmission problem.
    Then I would take that report to an Audi Dealer for the Transmission problem. If you live in a state which has a Dealer/Automotive repair shop certification program, first check the internet for a Certified Dealer or Repair
    shop that specializes in Audi.
    Hope this has been of some help. As you see there are many possibilities.
    Best regards
    jkaudiA6 :blush:
  • I was just told that the computer box was full of water, Is this a problem a lot of peopel are having? It there a defect in the Audi part that allows water to build up. My mechanic thinks it is from the ac nearby
  • Not sure what years this applies to but there was a successful class action suit against Audi based on this specific problem. The cause of the leak is a clogged passageway blocked by leaves or debris on top on the windshield wiper covers. This forces the water into the car and seeps down under the passenger floor to the transmission computer box. I wasn't aware of the cause and it destroyed my car, wasn't able to drive as well as developing mold. Not only was the computer destroyed but the cable harness as well.
    If you caught it early enough, you may be able to get a new computer board. Audi has a fix for the problem in there new maintenance program.
    Good Luck.
  • Water can damage the engine and other car parts. Parts such as the chassis can deteriorate extensively.To buy a used car can be risky, when buying a water damaged make sure your valuer guides you well.
  • Here is a link to one of several " Class Action suits" pertaining to water damage on particular VW & Audi products: sunroof-drain-andor-fresh-air-plenum-water-ingress-class-action-lawsuit-settleme- nt/
    To the original problem poster; The best you can expect from a group action is labor cost reimbursement. Periodic maintenance of drainage systems are generally not performed by dealer service procedures unless you specifically ask that it be done as part of a regular service; Noted on a dealer service work order. Water damage to the chassis is highly unlikely as Audi chassis is a unitized platform, of very specialized legierung ( combined metals) which are highly resistant to rusting. Additionally the chassis parts, after assembly, are completely submerged in sink bath before paint primers are robotically applied, resulting in the 12 year guarantee pertaining to rust. That being the case, and as previously mentioned, used car purchase should always be approached with caution and research. Some U.S states have additional "Consumer Protection Agencies" which can provide additional help should the dealer/Manufacture route fall to to provided help.
    The wire and control unit damage of the transmission are residual damage caused by a lack of periodic maintenance on the drainage systems. In closing it should be said the car purchased makes you the owner of the whole car with the exception of Software and related patents, much the same as with computers.
    I hope this has been of general help in approaching difficulties.
    Perhaps your car insurance might give some additional coverage options depending on policy coverage.
    Edmond's resources are many, take a few minutes and browse for specific info which might be of help.
    Best regards
    JKAudi A6 : :blush:
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