2.0 TDI Avant - Intermittent stall/no crank - relay diagram required please

[Hamodi1990]

Hi all,

My brother in law has a 2012 A6 Avant 2.0 TDI which has recently developed an intermittent problem. The car is randomly stalling with multiple errors showing on the cluster and also sometimes no crank no start then after a couple of minutes it would start up fine. I scanned the car when it was working and no error codes. Checked live readings and everything looks great. Seems to be an electrical problem. I also noticed that when it had the no crank no start, the scanner can't connect to the OBDII which makes me think it could be a relay or something supplying the ECM?

I searched online for a relay diagram but I only came across a fuse diagram for the A6 C7. If anyone is able to provide the location/list of the relays on this car then that would be immensely appreciated.

Also, if anyone is familiar with this issue and I'm going at it the wrong way in my diagnosis then please let me know!

Many thanks 🙂

[Magnet]

Hello Mohammed, 

Simple eliminations first:- worth getting the battery efficiency checked, before moving on to more complex possibilities. 
Perhaps you could let us know how you get on.

Kind regards,

Gareth. 

[Stevey Y]

2 hours ago, Hamodi1993 said:

Hi all,

My brother in law has a 2012 A6 Avant 2.0 TDI which has recently developed an intermittent problem. The car is randomly stalling with multiple errors showing on the cluster and also sometimes no crank no start then after a couple of minutes it would start up fine. I scanned the car when it was working and no error codes. Checked live readings and everything looks great. Seems to be an electrical problem. I also noticed that when it had the no crank no start, the scanner can't connect to the OBDII which makes me think it could be a relay or something supplying the ECM?

I searched online for a relay diagram but I only came across a fuse diagram for the A6 C7. If anyone is able to provide the location/list of the relays on this car then that would be immensely appreciated.

Also, if anyone is familiar with this issue and I'm going at it the wrong way in my diagnosis then please let me know!

Many thanks 🙂

Hi what did you scan it with software wise, if its one of the cheap hand held units it won't show anything of value, I agree  with Gareth as if the battery is dying it won't allow the OBD/Can gateway to function.

[Hamodi1990]

Thanks guys, really appreciate the quick response. The battery was changed only a few months ago. Also checked the battery voltage and seems good. Another thing is it wouldn’t make sense to me that it won’t crank then after  a few mins it works perfectly?

 

In my search for the relay diagram, I came across this YouTube video which shows the exact same problem and the relay they changed for the ECM. I will give this a try tomorrow but if anyone does see this post and have the relay diagram that would be super helpful!

 

[Magnet]

Thanks  Mohammed,

Sounds like you’ve boiled this down, and you simply want to progress along the lines of the video. That’s great.

Personally, I’d still want to work from my back-to-first-principles and get the battery (and alternator) efficiency checked to eliminate these before moving on, but your call. 
You ‘voltage seems good’ check done with a simple multi meter under no-load condition? 
Just out of interest - make of your battery? 
Kind regards,

Gareth.
 

[Hamodi1990]

Thanks Gareth.

Yes, battery checked with a simple multi-meter during no-crank-no-start conditions with errors on the cluster and again a couple of minutes later when no errors on cluster and car cranks/starts. It's a Bosch S5.

I have replaced the same relay as in the video and no issues since, so fingers crossed, but will continue to monitor over the next few days.