2003 Audi Rs6 limp mode on start up.

[Shoppinit]

You could always try disconnecting the engine mount to see if that makes any difference. It shouldn't but some electrical faults are bizarre and you both had an engine move by code. I think you can use a resistor to fool the ECU that the mount is ok but I don't know any more about that.

[simors6]

Thought I would add my tuppence to this thread for reference. TCU replacement sorted my fault.

[bilko1]

Where did you get your TCU ?

[simors6]

Was very fortunate as a forum memeber was breaking his Rs


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[blm70]

There was a few on eBay but £500-£600?!!! Ended up paying £235 from Lithuania! Chuffed to bits it's worked as it's been an intermittent problem since I bought the car over a year ago.

Got mine from ebay.de last year and paid around £300. Worked fine too.

Wonder what they cost from Audi?

When I was getting prices, the stealer advised me they cost £1100 and have to be shipped from Germany, assuming they have them; otherwise it's a case of waiting...

[Shoppinit]

I suspect it's possible to get a TCU for another 5HP24/A and flash the RS6 software onto it. Whether anyone knows how to do it is a different matter. Might be worth asking MRC or similar.

[srichards]

Would that ECU repair place in Heanor, Derbyshire not be able to repair it?

http://www.ecutesting.com/ They list gearbox TCUs as repairable. I'd start with them first.

[Shoppinit]

Update:

JT Automatics have now confirmed the TCU is definitely faulty, codes as below:

P0741-Torque converter clutch stuck off / no power transferred;

P1748-ECU checksum error.

They advised me not to bother sending it away as apart from re-soldering dry joints or basic components, the units were not repairable i.e. I could send it away, pay £200 + vat (the going rate), receive it back a week later 'repaired' to find it still doesn't work. This could be down to a missing or corrupt part of the programming that can't be fixed. Then I'd have an almost impossible job trying to prove they hadn't fixed it...

They had never come across a reliably repaired TCU either.

So the next option (and one they were in favour of) was to purchase a used working one from eBay. This is the one I've just bought and the seller did confirm I could send it back for a full refund (minus postage) if I changed my mind.

If I'm lucky this will fix the problem completely, or the TCU checksum error will be cleared but there will still be a gearbox problem...

Apparently, earlier models of this car had the TCU bolted to a piece of wood

Interestingly, they did say that in their experience torque converter issues were rare and only really seen in certain Range Rover models that use a similar transmission but are much heavier cars.

Still, until the TCU issue is resolved, they can't address any potential gearbox problems.