2012 A6 Intermittent start

[Rogerbluehat]

Hello, I’ve got a 2012 A6 that’s developed an intermittent start problem. Press the button and I get various “ stability program fault” and others. I’ve had it scanned it by Audi but they want £150 to do more diagnostic. I’ve read a few people have sorted this problem changing the ECU relay. Does anyone know what number relay I need to buy?
I’ve got the pages of the diagnostic scan but I don’t know how to add them on to this thread...

Thanks!!

[Crasher]

Yes it is the relay under the ECU in the plenum chamber water box, it is a well known problem with poor quality relays and there is a TPI about it specifically blaming a company called Tyco but I had one in with it a few weeks ago (not a Tyco relay that I could tell) and in his case it had gone from poor starting to cutting out whilst driving. We had it in for three days and it would not play up, a code read showed a near full list of red. I took it for a run to the body shop and it cut out on me just after a major junction on a busy A road and would not restart for about half an hour, very embarrassing.... The VAG part number is 4H0 951 253 A and it has 645 printed on top, it is a general purpose relay and this one is used quite a lot under the dash, they cost £20.68 from any VAG dealer. Considering VAG have been having ECU relay quality problems since at least the 1988 Golf 2 Digifant, you would think they could get their supplier issues dealt with at least on that part.....

[Rogerbluehat]

Yes it is the relay under the ECU in the plenum chamber water box, it is a well known problem with poor quality relays. I had one in with it a few weeks ago and in his case it had gone from poor starting to cutting out whilst driving. We had in in for three days and it would not play up, a code read showed a near full list of red. I took it for a run to the body shop and it cut out on me just after a major junction on a busy A road and would not restart for about half an hour, very embarrassing.... The VAG part number is 4H0 951 253 A and it has 645 printed on top, it is a general purpose relay and this one is used quite a lot under the dash, they cost £20.68 from any VAG dealer. Considering VAG have been having ECU relay quality problems since at least the 1988 Golf 2 Digifant, you would think they could get their supplier issues dealt with at least on that part.....

Thanks very much Crasher!

Been under the bonnet and have the 645 relay a tap and heard various positive sounding noises coming from around the engine. Car starts no problem. Don’t suppose you know if it’s the type of relay that Audi/Euro car parts etc would keep in stock?

[Crasher]

Buy a genuine one.

[Rogerbluehat]

Ok will do.. I’ll ring Audi in the morning.

[Rogerbluehat]

£17 from VW dealer. Changed it a couple of days ago and the cars been fine ever since. God knows what I’d have ended paying Audi if I’d let them sort it. Looking at the notes the mechanic had scribbled on the VAGCOM print-out they looking at changing the something in the ABS or a door control module. Either way they were nowhere near thinking it was a relay issue. God bless the internet.

Thanks