Mike Kramer

Does anyone know what may cause this? I've been having this issue for a while now, I've replaced the Speed Sensor (which was identified in a later CEL), I've replaced the Axle and still not sure where to go next. It seems odd that its only on Right Hand turns!?

Then, to make things even more confusing, some days it doesn't do anything! The next day, it gets triggered on every right turn and whenever I hit a bump! Any thoughts/experiences on that? Thanks in advance!

Grisho

I think this light comes on when (obviously ) the hand brake is pulled up, the brake fluid gets low and there is an issue with the brake possibly (maybe the owner's manual will show more reasons). It seems like the brake fluid may be just above the triggering point for the sensor so on right turns the fluid moves to one side and the sensor may activate. I may be wrong though, best is to read the manual and see what should activate that light first and go from there. Also what have you checked already?

Mike Kramer

Basically all summer, I've dealt with "ABS" and "Traction Control" light coming on simultaneously. Along with a CEL that pointed to the speed sensor, front driver side. So I replaced the speed sensor.

The next day, those two lights came back on. It was thought at this point that the Axle may be no good. So i bought an aftermarket axle from Parts Geek and installed, still same issue. At this point the Red Brake light chimed in. Now we're dealing with all of these lights at once. I took to dealership, and the guy who has worked on these cars when they came out in 2003 says "It's because the axle is aftermarket." I'm not so sure about that.

I found a new to me (used) Genuine Audi axle to re-install. I have a local guy who was a former Audi Technician looking at my car, he's got a plan to look into this deeper now. Electrical related.

I just wanted to stop in here to see if something so odd has been known for these cars. The Brake Fluid is within range, I'll look in the manual for what triggers the Red Brake light.

Thanks for your reply!

Grisho

No problem, I thought that you might know this already but just wanted to make sure. Indeed, I would never advise putting an aftermarket axle on the RS6. ~10 years ago I tried one, and it was about 20-30mm longer than the OE one I took off (when both are compressed) and it looked way different. Also used ones are not ideal either, but way better than a non OE one. If you are looking for recommendations: best is to repair your OE axle with a GKN repair kit (make sure it is a genuine axle first and this only works if your CV joints are not worn) (who ever does it must know how to do it properly, otherwise he will ruin your OE axle). #2 is to buy a whole axle from GKN (OEM supplier for Audi) if they have one for your part number.

Re: Brake light: might be worth checking the connector to the brake fluid reservoir level sensor too in case it is corroded, bad ground, etc..

P.S. (how I use OE vs OEM: https://www.turnermotorsport.com/t-OEvsOEM
(as even Audi USA (or at least their marketing team making their website) uses it "different" aka wrong

Grisho

Let me know what turns out to be the real reason, I am really curious (I had an Audi tuning/repair shop 2016 - 2023 and have been working on Audis since 2006 and I am super interested to know the real causes for strange issues as I may have them too (I am on my 2nd C5 RS6 now, that I'll never ever sell this time ).

Mike Kramer

Sure thing, will do! The axle that I got was GKN. My Audi Dealer said that is considered Aftermarket, even the advertisement said OEM, 2003-2004 Audi RS6 Axle Assembly - GKN Automotive W0133-1736474 - Front Left - PartsGeek.com

Mike Kramer

Since I thought the Brake Fluid was okay after getting it back from Dealership who performed a multi-point safety inspection, I assumed the Brake Fluid was good. My local mechanic who put hours into this thing just topped it off, said it needed some. He also installed my original Axle to get rid of the "Aftermarket" one.

Brake (Dummy) Light no longer flashes/beeps at me!!!

I got the car home, the ABS/Traction Control lights were still on (did not turn off automatically). I erased the code (P0501 Speed Sensor) and I'll see what tomorrow brings. After all the hours spent on this thing in past 5 months, I would kick myself if it was ALL just a result of low Brake Fluid!

Grisho

Wow, that is quite a story. It saddens me to say that this is definitely not the first time I hear something like this for an Audi dealer, actually I dreaded taking my wife's 2019 A5 in for a check engine light...
But yeah, trust, but verify

Grisho

Oh and it might be a good idea to bleed your brake system as it may have sucked air in. It might be a good idea to change it completely (you do change it every 2 years I hope ).

Mike Kramer

Grisho, I haven't forgotten about you. Still working on the problem. Soon, if you saw my radiator post, I will have my local mechanic put a new Go-Parts radiator in, at the same time do a Brake-fluid flush. I will confer with him about the "Axle rebuild kit" as I am interested if the metal ring on the end of the axle is the problem? I already replaced the speed sensor, maybe its the metal ring that is the problem? Per International Auto (Audi) dealership, the original 4B3-407-271J must be installed on the car to work properly. I removed the brand new GKN Axle per their request and re-installed the factory installed axle as suggested. Still same issue.

Maybe it's a ring thing!? lol, when I get it figured out, this thread will be aware.

Mike