gearbox tcu

[c4v8]

Hi all, just looking for some help with my rs6,
has been going into limp mode on start up for a few years , and just switched off and on again , without issue , so in the last few months has worsened , so off to chester transmissions who were very helpful , for a fluid change and subsequent soleniod swap , , has helped some but it looks like the tcu is suspect ,
there was another rs there and the tcu units were swapped over and the codes followed to the cars , so ,,,
does anyone have a good tcu i could swap over to help with the diagnosis , or a place ,to have mine checked and or repaired , or is there one available for sale ?
thanks
chris

[Shoppinit]

So they put your TCU into another RS6 and that one when into limp? And yours didn't?

[c4v8]

thats about it ! yes

[Shoppinit]

OK, just making sure because your symptoms sound a lot like a F125 switch and the TCUs aren't cheap.

Might be useful to say where you are located in case anyone has one they are willing to try in your car.

[c4v8]

im in shropshire , shrewsbury,
the car has been great for the last 7 years and 60 k ,
would it be prudent to go 125 switch before going down the tcu route?
thanks again

[Shoppinit]

When exactly does your car go into limp? Is it on startup or is it when you put it in gear?

[c4v8]

only ever on start up , never whilst driving ,

[Shoppinit]

Sure, but I mean is it as soon as you start the engine, or does it go into limp when you first move the selector lever?

[c4v8]

sorry , as soon as i start it , its immediately full block red on the dash selector icons, then if i select a gear , a big heavy clunk !
reminds me a lot of old rover p6 v8 borg warner autos!
so i usually switch off and on , quickly to "catch "it out , then its ok to go .

[Shoppinit]

OK. Do you have a Vagcom?

[c4v8]

yup sure do ,shall i get the codes?

[Shoppinit]

Yup.

[c4v8]

okydokey will sort that tomorrow, thanks for the input.

[Greegsy]

I had the exact same issue - previous owner had changed fluids, new F125 switch fitted and still the same. On startup all gears lit up on dash and was very clunky selecting a gear. The cure was to switch off and back on again and then was all fine. I took a chance buying the car like this and was pretty certain it would be the TCU. Managed to source one locally and yep been spot on ever since after swapping out TCU. Some signs of slight corrosion on the PCB on the removed faulty TCU. So could be water ingress within yours maybe?

[c4v8]

hey thanks for that , i sorted the water issue when i bought the car some years ago and it has stayed dry , but old car, old solder and the joints do go ever so gently over time ,
codes a coming !