F125 Switch or TCU - or something else?

[Duke Thrust]

Thanks - are there two connector types?

(Just called Audi and they're after 192+vat)

[HPsauce]

Best investment you could make is to buy a genuine VCDS cable. Saves on guesswork.
Then you can really see what's going on, clear codes and see how quickly if ever they reappear.
F125 costs a similar amount and is a pig to get at, though not as difficult I'm told as on an S8 (which is a very expensive job if you can't do it yourself).
And surely yours will be the later 10-pin (oblong-ish) version, not the early 8-pin one (which is round)?

[Mɐʇʇ]

You can double check here https://ifinterface.com/page/page3.php?langid=1
Choose CarProg2=>Audi=>Europe=>RS6=>2003=>9=>927-090 and it's item number 7

[HPsauce]

Just a follow-up re the F125. It has a bunch of mechanical circuits inside, with moving arms wiping spring contacts over arc-shaped conductive tracks with gaps.
Horrible thing, but debris from one track can easily interfere with another, then move away as you change the shifter position.
So even if you "know" where the problem is, the cause may be elsewhere and another circuit can totally fail first.

As an example my current F125, which was new not that long ago, was giving odd errors but then suddenly the car wouldn't start. The starter/inhibiter relay circuit had finally broken but the debris from it had been interfering elsewhere for some time.
Still not taken it off to investigate, I've just bypassed the circuit by replacing a relay with a jumper for now!

[Mɐʇʇ]

When mine failed, I took the cover off and could see the exact bit of corrosion on the tracks that was the problem. I've kept it, since, if push came to shove, I think it could be cleaned up and pressed back into service - but for now, new is good.

[Shoppinit]

Yup. Get it from Audi / TPS. No brainer. The 01L obvs.

[Mɐʇʇ]

"The right one, obvs".

[Duke Thrust]

Thanks guys!

I'll think I'll go via the modification of the gearbox mount as per the bottom of here: viewtopic.php?t=116756 (unless not recommended)

[airtite]

yup my issue is the switch noticed my reverse lights arent coming on... found this with the pin outs for the f125 switch

https://www.audizine.com/forum/showthre ... lease-help

Pin 1 is black/red and is switched power from fuse S114 for the switch.
Pin 2,3 & 4 go the TCM (white, yellow/white, grey/green respectively).
Pin 5 is brown/green and runs to the ECM.
Pin 6 is brown and is the ground for the switch.
Pin 7 is blue/red and is the output to the reverse lights.
Pin 8 is black/blue and is switched power from fuse S14.


I have a stupid rattle coming from the right hand side near the down pipe that I cant track down... its not mechnical ie with the motor off and banging on the downpipe from under the car I can here it but I just cant get too it, so I am probably going to do another motor pull and then sort out both the rattle and the f125 "fun days"

[HPsauce]

You might find the attached picture of the inside of a10-pin F125 useful.
It has the tracks/pins labelled. Something I did when bored a while back……….

[Shoppinit]

Looks so '70s tech.

[HPsauce]

You should see the twin arms that move over those tracks! Very 1940s.....

By the way I think pin 6 is not just unused, it's actually not present in the F125 cable plug.

[Mɐʇʇ]

Here's the inside of my failed one, too. I assumed it was pin 8 that was causing the error?
Did consider cleaning it up & refitting - but the cost of the the switch compared to the aggro of replacing it wasn't worth it.

[airtite]

can someone please posrt the part number for the one for the rs6 please?

[Mɐʇʇ]

It's highlighted in the screenshot I posted earlier in this thread. 01L something