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Audi A4 2.5TDI Quattro automatic gearbox help needed

Discussion in 'A4/S4 forum(B5 Chassis)' started by Alibi, Jul 28, 2010.

  1. Alibi
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    Alibi New Member

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    [Jul 28, 2010]
    My car suffered water ingress due to a drainage pipe getting blocked with leaves - the result was that the area where the battery sits in front of the windscreen filled up with water to at least the underside of the battery - the water then found its way into the front footwells through the bulkhead which is what alerted me to the problem (also occurred on my previous A4 so seems to be a design fault). Anyway, the water appears to have affected the electronics controlling the tiptronic gearbox. For a short time the car went into a sort of limp home mode where the throttle didn't react and the car would only move at idle speed. After a few hours, it worked again, but when I switch of, all the lights on the gear selector indicator on the dashboard light up at once, and using the manual select facility has no effect. I thought it might fix itself once it dried out but so far it seems to be a permanent fault. Can anyone advise where to start looking - I suspect there will be some sort of plug in electrical unit in the space near the battery that has been soaked. I should add that the gearbox works after a fashion in D and R although when you select them there is a jerk, and also it won't get into fifth - 40mph it's still doing 2000 rpm which is what it usually does at about 60rpm. 5th usually cuts in at about 37mph. Car also a wee bit slow to pull away with more slip than usual.

    Help!!
    Last edited: Jul 28, 2010
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  3. adamss24
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    adamss24 Well-Known Member

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    [Jul 29, 2010]
    I would check the ecu first as there are terminals wich corode without water getting in then check/replace the gearbox control unit with a known good one...
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  4. Alibi
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    Alibi New Member

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    [Aug 12, 2010]
    My garage has had the car in for about 2 weeks now with no success. I told them to have a look at the ECU which I was told was under the driver's seat and thus had probably been underwater for a while. They took out the driver's seat and didn't find an ECU. My question is: where is the ECU located? I would stress it's a tiptronic box, not a multitronic (which I think only appeared in 01/02 or thereabouts). The garage now thinks it might be on the side of the gearbox but I suspect they are confusing it with the multitronic set up where I understand the ECUs were on, and later in, the gearbox.

    This is getting a bit exasperating now as nobody seems to be able to fix it. i am a wee bit concerned that having just fixed everything that needed fixed, the car might now be useless and only fit for a serious fire. Sorry, I meant to type "scrapping".
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  5. murran
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    murran Active Member

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    [Aug 12, 2010]
    think the gearbox ecu is in a plastic box on the floor under the carpet in the passengers foot well.
    when all the driving position lights on the dash pod it usually points to the "range sensor" on the side of the gearbox. this might be what your garage is on about. but with the ecu getting wet id say to go for that.
    get the part number off the ecu and get a second hand one. it'll need coding in tho.
    does your garage have diagnostics?
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  6. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Aug 12, 2010]
    Not trying to be funny but are the garage complete mongos?

    Follow the bloody wiring harness, its about an inch thick.

    It IS under the drivers seat, but its not just floating around, you need to lift the front edge of the carpet etc, ie its mounted in the floor, inside a black box.
    Last edited: Aug 12, 2010
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  7. Alibi
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    Alibi New Member

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    [Aug 13, 2010]
    My garage said they removed the driver's seat and still couldn't find it. They are usually pretty good - it's a small independent garage but they have diagnostic equipment and all that stuff. I know that wiring harness - it continues to the rear footwell.

    I've given the garage all the info I have and they're having another go at finding the box today - I can't fathom why they thought it necessary to remove the seat as I assume at a pinch you could just cut the carpet under the seat area. If they give up, I'll do it myself, or if all else fails there's still the option to take it to an Audi dealer in Carlisle.
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  8. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Aug 13, 2010]
    Well, its not actually under the seat. Its in the footwell just infront of it, so your right, the seat doesnt need to come out, just remove the trim and lift the carpet.
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  9. Alibi
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    Alibi New Member

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    [Aug 16, 2010]
    Sorted. They got the ECU out and after leaving it to dry out properly over the weekend, the gearbox is now working fine, with the only remaining glitch being that the D light is flickering occasionally - I expect that to right itself once the car's been driven and a bit of warmth gets to the ECU from the heater and maybe a bit of heat soak.

    I did suggest putting the unit in a vacuum chamber to get rid of all the moisture quickly, but you can never find a vacuum chamber when you need one.

    Thanks all for your advice.
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  10. Alibi
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    Alibi New Member

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    [Aug 23, 2010]
    Just noticed that not only does the D light flash on and off, but the 54321 display on the tiptronic manual mode also flashes between 54321 and PRND4321, and I can't select gears manually. It's not a big problem in practice as the auto function seems to be working fine, but it would be nice if it sorted itself out. May have to resort to cat litter to dry the ECU out fully...
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  11. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Aug 23, 2010]
    silica gel would be a better choice imo.

    You may find it will never be right though, over the years i've had a few mobiles that got wet, and while they still worked, they were always a bit wacko afterwards, with random lights staying on and things.
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  12. Alibi
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    Alibi New Member

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    [Aug 30, 2010]
    The ECU has obviously fully dried out now because the D light no longer flashes and I have the full 54321 manual over-ride function back. Result. If it happens to anyone else I'd suggest lifting the carpets, sponging out as much water as possible, and putting the ECU in your airing cupboard for a day or three. Possibly drilling a few ventilation holes in the casing might speed up the process.
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