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Haldex ECU - Fault Code J492

Discussion in 'A3/S3/Sportback (8P Chassis)' started by Jonay, Sep 23, 2011.

  1. Jonay
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    Jonay Member

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    [Sep 23, 2011]
    I've got the ESP light on on my dash - fault code J492 which my local garage didn't want to touch "take it to audi - the haldex system isn't something we know how to deal with"

    I googled the fault code - it appears to be the J492 - no signal to the ECU.

    It can either be due to a loose connection (it was flickering to start with) or a dirty/corroded connection.

    Anyone else had experience with this?
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  3. Adamantium
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    [Sep 23, 2011]
    Yep!

    Mine was turned off this morning for the first time after buying the car.

    In my case the ecu was screwed. It had a hole in it and severe corrosion to the circuit board itself.

    Before determining this was the cause and searching for one on ebay, I did research to determine if I could diagnose it. Typically the problems that cause the fault you mention are corrosion of the pins inside the multiplug that connects to the haldex ecu itself, and corrosion of the earth point of the loom which is attached to the rear subframe.

    Check these first. If it these don't solve it, you are probably best off just replacing the ecu like I did.

    You then need to determine if you have a gen 2 or gen 4 ecu. This is determined by the age of the car. Pre 8p3 they were gen 2. This is the same as the mk2 TT and the Golf mk5 4 motion or R32. If your car is pre 2008, it is likely to be gen 2. You can determine for sure by reading the code on the bottom of the haldex diff unit. If it is OAV it is gen 2. If its anything else it is gen 4 (there are three options I think one of which I recall is OBV but can't remember the others ).

    The gen 2 and gen 4 Haldex ecus look identical to one another, but they differ in firmware and cannot be interchanged.

    FYI gen 3 was reserved for some and saabs.

    If looking on ebay try to pay under £200. Most sellers don't list them separately and sell them with a complete rear diff. Search for golf, quattro or TT rear diff.

    Took me ages to sort this out, but got there in the end. The part from audi was £800. I also tried people who had upgraded to the performance haldex controller but never managed to find any or at least not from the correct gen diff.

    Hope this helps.

    Good luck with your search!
    Last edited: Sep 23, 2011
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  4. Jonay
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    Jonay Member

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    [Sep 23, 2011]
    Thanks I've just come across your thread with the reference pictures posted by the other user.

    You say you had 4 potential suppliers - do you still have details?

    I'll need to get down into the pit Sunday morning and see what the status is.

    Honestly the lights been on for months - though with my MOT coming up it's only really got my arse into gear! I think the snow last year might've got the better of it.
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  5. Adamantium
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    [Sep 23, 2011]
    it wouldnt be an mot failure, but I'd want it sorted pre snow!

    Two of them turned out to be Gen 1 so no good. That left two on ebay. One I bought, the other had sold two weeks before with a rear diff for £425.

    That reminds me, the haldex ecu is no different if connected to a diesel or petrol car, you can use any one from the correct year.
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  6. Adamantium
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  7. Jonay
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    Jonay Member

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    [Sep 23, 2011]
    Nice one thanks.

    I have my MOT tomorrow. I did notice that traction control wasn't a tested item.. I'll ask them if they could grab the serial code whilst they've got the car up on the stands.
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  8. Adamantium
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    Adamantium Member

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    [Sep 23, 2011]
    how old is your car?
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  9. Jonay
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    Jonay Member

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    [Sep 23, 2011]
    its a 2006, 55 regplate
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  10. Adamantium
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    [Sep 23, 2011]
    Gen 2.

    any of the links I sent you will be fine.
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  11. Jonay
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    Jonay Member

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    [Sep 23, 2011]
    Nice! thanks for that! You're saying just to buy the whole unit and take the ECU off? or to ask them to just send the ECU?

    Hopefully this MOT tomorrow doesnt cost me a bomb! (I think i might need a siezing O/S/R caliper+ pads replaced)

    EDIT : Just noticed that last one says "stamped on the lower side - XX OBR XXXXXXXXX"

    Thats a Gen4

    http://www.hpamotorsport.com/images/drive/Haldex-Identification.jpg
    Last edited: Sep 23, 2011
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  12. Adamantium
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    [Sep 23, 2011]
    check your electrics first.

    If they are fine, then buy a new one. If you can get them to sell you the ecu separately you are doing well. They wouldn't for me, and last week there was none advertised for less than £200. I had to pay for the whole diff and tell them to throw the rest away!

    Not sure where you are talking about OBR, but yes that would be a gen 4.
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  13. Jonay
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    [Sep 23, 2011]
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  14. Jonay
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    [Sep 25, 2011]
    I might have a Gen4 Haldex - my code is OAY

    [​IMG]

    Here's my code is here as clean as I could get it at the time..

    [​IMG]

    I took the 2x Hex head bolts out - to gain better access to the cables - I pushed them in so if they're loose it might help - it didnt.

    Is oil supposed to come out?

    [​IMG]

    [​IMG]


    I couldn't see anymore cables - nor could I see where these cables routed..
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  15. Jonay
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    [Sep 25, 2011]
    Ok I've been looking around, and yes oil is supposed to come out as its got a couple of oil pressure sensors (the one that's sticking out the unit I'm holding - the other one is still inside the diff).

    I just need help with where the cables route to disconnect it. (at the other end)

    And I'll also need to change the Oil/Filter in the Haldex once it's fixed - its black!

    Still is dispute about the code on the base of the Haldex and therefore the Gen. AmD's website doesn't help

    AMD Technik UK - All copyrights AMD Technik Limited 2010
    Last edited: Sep 25, 2011
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  16. Adamantium
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    [Sep 25, 2011]
    If there an a in the middle it's a gen 2. Your car is too old to be a gen 4.
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  17. Jonay
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    [Sep 25, 2011]
    There is an A - but it really does look like a Y at the end there.

    As for the cables - did you mean the corrosion to be on the lead or on the multi connector on the ECU itself?
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  18. Jonay
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    [Dec 18, 2011]
    Just replaced the Haldex ECU and it worked first time. Thanks for all the help!

    Couldn't be happier! Just in time for the snow too!
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