Nightlifephantom

2005 4.2 S-Line


My car has been sitting at the shop for about a month, give or take.. The battery was dead when I tried starting it, so we charged up the battery, car started fine but the MMI screen will not turn on. We ended up putting a brand new battery in and still the same issue. Everything was a 100% working before we took the oil cooler off to change 2 O-rings. The threads that I've read point to an optical/control head issue... but again everything was working fine before the battery died. Anyone ever encounter this? Or know of a remedy?

raj99

Most likely when you jump started the car you blew a fuse which caused the MMI to become inoperable. Check the passenger side fuse panel right on the side panel and you'll see a fuse related to radio/MMI function. That's where I would start and also run a VCDS to see if there aren't any other things going on.

Nightlifephantom

Running a scan was one of the first things I did as well as MMI 3 button force restart. A ton of stuff was outlined in red and stated malfunction... actually the majority of everything was. Seems like everything related/tied to the MMI failed. I ran a optical bus diagnostic as well.. had a couple of errors... Control head, Navigation, radio and a few others. Can't actually post the full scan at the moment. But seems very weird, was curious if anyone else encountered this.

You don't think modified headlights would have anything to do with this, right?

After extensive searching, I realized that you had a similar problem a while back:

https://www.audiworld.com/forums/a6-...2873702/page2/

My aim later today will be checking all fuses again and going from there.

Nightlifephantom

Ok. How do I code the battery? I know how to do it through VDCS but the brand of the battery is AutoStart. I don't see it as an option in the list. Anyone know how I go about this?

raj99

Sometimes you can get by with changing 1 character in the serial number and it'll suffice:
https://www.audiworld.com/forums/a6-...cment-2879428/

Battery Replacement - Ross-Tech Wiki

Nightlifephantom

Ok, still the same issue. No power to MMI at all and a bunch of red highlighted modules in VDCS.

raj99

Did you thoroughly check ALL fuses? Do you have a fuse tester?

BTW, what do you mean by modified headlights?

Nightlifephantom

Started raining here, going to wait for it to stop to go back out.

By modified headlights, I removed the AFS unit internal/external from the right stock headlight, the left headlight was replaced recently by previous owner with no AFS, and I also added a DRL LED strip to both headlights

Nightlifephantom

Good news. I fixed the issue. The shop checked the fuses with a tester, I did the same after I got home, then after it rained I decided to check them all one bu one y pulling them out. Sure enough, it was the same exact fuse as in your previous thread that I posted. Communication Fuse.

raj99

Occam's Razor ...glad to have helped.