Update - solved the issue.

Upon reading other threads I checked the ABS wheels speed sensors on all 4 corners.

The front passengers side sensor was damaged. A break in the sensor case was letting water into it. I’ve replaced the sensor and the faults have all gone away. 
It was a bit of a pig to change as it’d melted into the bearing housing.
Quite a coincidence that the wheel bearing was changed by the garage a few weeks before all these faults started appearing. 

Hello all, new to this forum and am appreciating the detail this thread has gone into. 
 

I have found today (08/12/2025) my A6 Allroad has flag up lots of faults on the dash, before this happened I did notice a slight slide on some mud before I stopped and parked my car, note also we had persistent rain recently. Coming back to my car to drive home (short distance from dog walk location) note i have multiple warnings on dashboard like a Christmas tree but not wanting to reference the link to the expense of Christmas 😂

 

scanning through this feed and noticed similar symptoms/problems but could never source the root cause, one found speed sensor, one found moisture in boot, one mentions battery health  

 

I’ve had a new battery installed about 2minths ago in an Audi specialist garage, coded to car, same as original. No known moisture in the boot area, though I will check again. Reading the thread it may be a voltage drop that’s triggered these faults but the hive mind here maybe able give some guidance 

 

would soooooo much appreciate your wisdom 👌 in this matter  

Edited December 8, 2025Dec 8 by Wrenner

Update, I’ve started to take apart boot area and have found lying water within spare wheel/battery bay, within the spot welded structural body of this area, noted a previous comment on this thread about a voltage unit (not sure of the name) but needed drying ?? And source hole to plug. 
 

keeping people and thread updated on what I find so it helps future symptoms and diagnostics 

Post felt removal, I’ve noticed the moisture and level of is v low, underneath lighting holes of bent tin structure, suggest water pooling locally 

 

I’ve had a garage (quoted in original post) replace battery, out of curiosity is there any features underneath battery that would allow moisture ingress ? Bolt holes or drain plugs ?

 

also note (as mentioned in the original thread by someone) the joints on the rear face of the bay are unsealed (some pictures to show this attached)

 

im thinking I might seal this joint up as I can see remanence of moisture in the joint 

Thomas. If you read the whole thread you will see that Paul Cairney had very similar warning messages to you and that he found a solution.

Yes I tried to follow threads but I may have got lost on it all, newbie 😬

 

Ill track back and search for this one 

thank you for your reply, much appreciated 

Update. After sealing all know gaps around the spot welded sub structure to rule out moisture ingress though this I noticed 2 of the drain plugs were still damp, then noticed the sealant or glue used to properly seal these in place was degraded and thus could cause a leak into the battery bay, sealed this back uk also. 
hopefully this along with drying out area and drying the DCDC module will sort it out 

 

still not sure whether the system will just reset itself or do you need to complete some kinda reset 

On 3/26/2024 at 10:24 PM, Jonny G said:

Thanks yes, saw that thread. It seems a common issue with the C7, they like to let water in as much as possible.

Further investigation this evening and I narrowed down the leak. See the picture attached, but the leak is coming through a seam in the side wall. Circled the area in red.

I have sealed this area with Gorilla waterproof patch & seal tape.

I removed the Voltage stabiliser unit to dry it out, and also moved the wiring loom for the Voltage Stabiliser unit up and back out of the spare wheel well up into the area where the main fuse board unit is. 

I hope that these two actions will cure the problem. 

Hi @Jonny G. Did the drying out, sealing and reinstallation cure the issue for you ??

did you have to also do any onboard resetting of systems ? Or did the basic car check (when ignition is on) sort the issue ??

 

I’ve done similar, sealed areas looking like potential problems, dried out module  by disconnecting and drying out in house. 
 

Post reinstalling the module, the faults still pop up on dash though moving the suspension actually works so think it needs a reset

 

can you elaborate on post sealing, did it fix your problem totally ????