Electrical issue now SMH

A6 All/ S6 All
#1

Hello, its me again, after replacing a blown fuse, changing the oil cooler, cleaning or changing all injectors and finally chagin the alternator, the car ran amazing and even better than before! for… 6 days or 250kms before another problem!!

Now it seems to be a strictly electrical issue, yay, just what I like!

From the codes it throws, its like a fuse blew as many many codes show up, but I dont think the fuse actually blew.

I replaced the fuse that blew last november with a cheap non-OEM fuse (amperage is correct). Could that be it?

After letting it sit for a while waiting for the tow-truck, I could start and even drive onto it fine, and it ran perfectly without any roughness. Could the heat expand the material enough for the non-OEM fuse to not actively touch both sides and cause it to error?

The only other thing I can think of is a persistant code that has been there even before all of my recent issues: a steering angle sensor related passive fault. If I remember correctly, my car stalled twice after throwing the usual EPC/ESP fault after turning my steering wheel almost to the end. Sensor is faulty and shorting causing the electrical system to trip? I might be reaching there.

I’ll start by getting an OEM fuse and changing it, but I will also buy the steering angle sensor since its faulty anyway and not costly.

If any of you have other suggestions, please say.

#2

Did it start doing it after car got warm? And it doesnt do when its cold?

#3

yes it did start, then stalled after a couple of seconds. I dont really know if it does it when cold, I could only drive it 250 kms before it started doing that, but waiting for the tow truck seemed to be enough time to be able to start it without stalling and even drive it a bit. I dont know how far I would have gotten though

#4

It got to be a relay. I had the same exact issue. It drove me nuts. For my situation one of relays was so hot it burnt my finger which made it obvious

#5

Where was it located? Fuse box below the hood?

#6

I remember it being the one under the hood. But it can be the one under the steering wheel as well. I think it was one of ecm relays

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#7

This sucks. Keep us posted. Thankfully sprawwl has had tons of stuff go wrong so he’s going to have a lot of time on job for the odd issues.

#8

Changed both relays under the hood. But it still does it. Weird thing is that it only does it when hot, at idle or going slowly, and when I stall, I can get out, switch both relays around, and then I can leave again. As long as I dont stop a lof, it usually doesnt do it again.

#9

Definitely strange did you check the relays under the steering wheel?

#10

Under or on the side?

#11

Under

#12

I was told with the freeze frames and codes all either saying lost communication/no voltage/voltage spike, it is either a bad ground, or a connection in my ecu is seperating when hot. Does anybody have a diagram of all the grounds that would be linked to this series of sensors? Grounds of the in-engine bay fuse box, ecu grounds, etc.

#13

C6_S6_Ground_Locations.pdf (2.2 MB) C6_S6_Ground_Locations_1.pdf (455.1 KB)

I have something like this. Found it on this very forum some years ago.

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#14

I’d double-check every fuse you touched, especially the non-OEM one, and make sure the amperage matches what the car expects. I’ve had mystery electrical chaos from one cheap fuse before. I once used a diagram that showed the trunk fuse box location, and it made spotting a bad connection a lot easier. Also wiggle-test the grounds near the battery and alternator; a loose one can throw a ton of random codes.

#15

I replaced the cheap fuse with an OEM one already, and it didnt change anything. Ill try wiggling the grounds, but since it happens only when hot and idling, i believe in the worst case scenario which is one of the ecu is internally failing. A connection gets loose with heat expansion and disconnect for a fraction of a second with idle vibration. Ill send it to a shop for them to diagnose the problem, im ass in electrical work.

#16

Still give the relays under the steering wheel a shot if you haven’t before you send it out.

#17

And how could I do that? Theyre only faulty when at operating temperature and after idling for like 5 minute? Ive done 30+ minute highway travels at temperature + stop and lights and nothing. Only does it when stuck in traffic or idling in my driveway. I cant just test them to see if they click or work, cause they will until they lose connection for a fraction of a second, but a fraction enough time to confuse the ecu. Thats if the relays are the problem.