Audi A6 (C7) no ignition power

   #1  

spude

Verified VCDS User
Verified
Joined
Aug 27, 2018
Messages
1
Reaction score
0
Location
Finland
VCDS Serial number
C?ID=331195
Hi,

newcomer here. I hope to find some help as I´m currently puzzled. I have fixed quite a bit mechanical issues in cars generally, but I´m not an expert in electricity stuff.. so please forgive me and guide the helpless :)

Brief background story: The car is an Audi A6 (C7, 4G) 3.0TDi (MY2012). Last week, while I was changing the glove box bulb, the interior lights went off and I heard I faint snap sound from the drivers side. Well, thought it´s the fuse. After few hours (!) of searching, I finally located the bad fuse next to the steering wheel axle under the plastic cover and changed it. The interior lights went ON.

However, while I was trying to start the car by pressing the START/STOP button, nothing happened. No ignition power, no lights to odometer, or anything else. I triple-checked all the fuses I was able to find by measuring resistances, but everything seemed to be OK. I inspected visually all relays next to the fuse boxes and measured resistances, but couldn´t figure out anything that would indicate a bad relay (they still might be bad, I´m just not familiar how to correctly test them). The main fuses in the battery end were also OK.

I hooked up the car with VCDS, but the auto-scan was able to read only CAN gateway (probably because there is no ignition power) and no fault codes there. Well, then I was suspecting bad battery, as it was already 6.5 years old, experienced rough winters, not charging properly, and I had some previous observations pointing towards it. However, the voltage was still OK(ish) (around 12.4-12.5V), but decided to give it a try. I changed a new one (and updated coding via CAN gateway), but it did not help (car was without battery for some time).

Then I read about the trick (brake+emergency flash+pass by lights) to get access to the module 05. It actually worked, and I was able to read the fault code "02811 - Control Module for Electronic Steering Column Lock (J764) - 004 - No Signal/Communication", which returned after clearing codes. Looked also the measurement blocks, but they did not tell me much as not many of them had a clear description.

I started to suspect again that there is a bad fuse or relay, and went back to fuse boxes. I found out that the first panel (A, black) in drivers side fuse box, and the last panel (D, green) in trunk were not powered up with 12V, while the rest of the panels (including passengers side) had 12V on. The panel A in drivers side seems to be quite essential for ignition and stuff.

Long story, but at the moment my main questions are that should all the fuse boxes receive 12V without ignition turned on? And if they should, are there certain fuses/relays controlling them that I haven´t been able to find or which I should try to recheck/change? And is the fault code a clue, or is it just a sign of lack of power in the system? Or any other thoughts what should be done next, for example related to the measurement blocks in module 05? The car is sitting in my garage with electronic handbrake on, and automatic transmission in P position, so it is not willingly moving anywhere (nearest Audi service 20km away).

Thanks in advance.
 
   #2  

Uwe

Benevolent Dictator
Staff member
Joined
Jan 29, 2014
Messages
30,520
Reaction score
21,775
Location
USA
VCDS Serial number
HC100001
Long story, but at the moment my main questions are that should all the fuse boxes receive 12V without ignition turned on? And if they should, are there certain fuses/relays controlling them that I haven´t been able to find or which I should try to recheck/change?
What should and shouldn't have 12V on it at all times, and what fuses and relays may prevent 12V from being where it should can best be determined by careful study of the Wiring Diagrams for your specific car.

-Uwe-
 
   #4  

jimmyq

Verified VCDS User
Verified
Joined
Sep 3, 2014
Messages
55
Reaction score
11
Location
UK
VCDS Serial number
C?ID=139879
hi did you manage to fix this problem ?
 
Top