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Thread: A8 [D3] & A6 [4F] Battery ECU compatability? ...

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    Question A8 [D3] & A6 [4F] Battery ECU compatability? ...

    Does anyone who looks after various Audi vehicles have any experience of whether the A8 [D3] and A6 [4F] battery manager ECUs are compatible?

    Or perhaps someone has access to an A8 and an A6 and can quickly swap an A6 one to see if it works in an A8?

    That is; Can I use an A6 ECU [part number starts 4F0] in my 2005 A8?

    For some reason, although they look identical externally, and functionally participate in an 'identical' MMI system, A6 ECUs are cheaper 'second hand' that the A8 ones!

    Julian

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    Ross-Tech Employee DrPeter's Avatar
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    Does anyone who looks after various Audi vehicles have any experience of whether the A8 [D3] and A6 [4F] battery manager ECUs are compatible?
    Hi there ... Even though the parts look identical and they may even share the same internals, the part number is different and I would say the two are not 100% compatible.

    You may have noticed that many VAG parts are used in different vehicles, like the R8 for example, my A3 shares quite a few parts with the R8, these part numbers are exactly the same. And that is the thing, you can interchange these without worries, but exactly the same looking parts with different part numbers, I would be careful, the manufacture does not make it public all the differences between the two and if they were to work in other applications (A6 / A8), they would most likely have the same part numbers like the R8/A3, it appears they do not hide this fact, just don't tell the Bentley owners they are really driving a W12 VW Beetle


    Hope this helps,

    drpeter

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    Thanks DrPeter; I must admit I was suspicious that they would 'match' but their functionality is so similar I can't quite work out how they'd differ. Hence the 'has anyone tried' request.

    BTW, I have noticed part number sharing as a lot of the A8 stuff went into A6s [and other cars] and kept the 4E0 prefix; they were presumably 'plug compatible' in all the cars. But I've seen A8s running A6 Bluetooth modules [4F1 862 3356] although there is an A8 BT moduile [4E0 862 335]. Thus an A6 part is running in A8s.

    The reason I was 'checking' the possibility of a swap is that I suspect my 'firmware updated' A8 BEM is not functioning properly [It was updated via a VAS5** in response to an Audi TSB some years ago; it went from 0390 to 0510]. But I NEVER see any DIS messages about the battery or the shutdown stages even though I get DTCs in the ECU reflecting those issues that I can see with VCDS.

    But a replacement is now on hold awaiting the very recent news of Uwe's possible development of a BEM Log reader function in VCDS ...

    Julian
    Last edited by JulianHicks; 02-10-2017 at 02:59 PM. Reason: Typos

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    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by JulianHicks View Post
    The reason I was 'checking' the possibility of a swap is that I suspect my 'firmware updated' A8 BEM is not functioning properly [It was updated via a VAS5** in response to an Audi TSB some years ago; it went from 0390 to 0510]. But I NEVER see any DIS messages about the battery or the shutdown stages even though I get DTCs in the ECU reflecting those issues that I can see with VCDS.
    Yep, the early 4E/4F cars "cried wolf" about the battery a lot, which upset the car's owners, so Audi dumbed the whole thing down with software updates.

    Quote Originally Posted by JulianHicks View Post
    But a replacement is now on hold awaiting the very recent news of Uwe's Eric's possible development of a BEM Log reader function in VCDS ...
    Fixed that for you.

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    Oh does the latest version of VCDS have access to these logs now?

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    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by delboy View Post
    Oh does the latest version of VCDS have access to these logs now?
    No, not yet.

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    Thanks for the reply, will it be anytime soon, I understand there is probably not many users interested in it as a feature but it sure would be nice for me.

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    Ross-Tech Employee Eric's Avatar
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    We'll push out a beta as soon as it works well on the two cars we have here (B8.5 S4 and 4F A6). I just got the A6 on Friday and there's work to be done to accommodate the arcane ways in which it sends the info.
    You ain't metal till you got a clutch pedal

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    Verified VCDS User Zenerdiode's Avatar
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    Thanks Eric. You know I've been (patiently) waiting for this for a long time.

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    So backwards step may help? ...

    Quote Originally Posted by Uwe View Post
    Yep, the early 4E/4F cars "cried wolf" about the battery a lot, which upset the car's owners, so Audi dumbed the whole thing down with software updates.
    Uwe
    Brilliant

    So instead of fixing the issues they turned off all the messages.

    Your comment, Uwe, explains why I used to see some messages [firmware 390] and never seen any since [firmware 510].

    So I've bought a cheap 'early' BEM [firmware 0160 - from early 2003] which I'm going to fit and recode to see if I get any messages about what's going on with my car' battery system.

    Julian

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