Q7 Turning off when driving and wont start when warm

[Sarah86]

Hi everyone, I was hoping someone could help me solve some issues I am having with my Q7.

2007 Q7

4.2l TDI

The car starts and drives fine when cold in the morning, but all of a sudden an ESP fault flashes up and cuts the power to the engine. We try to turn it back on, but it just turns over but dosnt start. The next morning the car will start again with no problem, but then the issue happens again. 

Today I left the car running and parked up for about 10/15 mins, when I went back to the car, it has turned itself off. I then turned the key and it turned back on fine, left it for a while with no problems. I turned it off and on again and it wouldnt work!

I don't know if this is possibly 2 different problems? From what I can see online it could be a problem with the Crankshaft sensor not letting it start when hot?

The only code that pops up is a exhaust sensor, but I dont think this would cause these problems.

If anyone could help with where I should start with these issues, or have had similar problems in the past, please let me know.

 

Thanks, Sarah

[Magnet]

Hello Sarah,

Thanks for joining and sorry to hear of your issue. 
I always approach any persistent warning light problems and associated issues, on the basis of a simple and cheap elimination process before moving on to more expensive investigations. 
Culprits for warning lights can be the battery, and its efficiency can be simply and cheaply ( even free!) assessed at your local Halford’s store. Their test is usually pretty comprehensive and results in the battery being declared serviceable or not. At that point, you will then be armed with evidence to exclude the battery efficiency as being a contributor or not. Ask them to check the alternator output at the same time. 
If the battery is declared sub standard, then personally I would not be tempted to buy a new battery from them at that stage, but come back to us with the result. 
OK, even if the battery is replaced, it may not solve the issue, and further more expensive diagnostics might be necessary, but an efficient battery is essential for any ‘modern’ vehicle. 
Perhaps you could let us know how you get on. 
Kind regards,

Gareth. 

[Sarah86]

Hi Gareth, thanks for your reply!

I have only just put a new battery on it about a month ago, as the car was sat for a while. I am happy to take it to Halfords to check the battery and the alternator at the same time, as long as I can get there before it breaks down again!

I will let you know how I get on

Thanks, Sarah

[Magnet]

Thanks Sarah,

Sorry, but we didn’t know that. 
Make of battery as a matter of interest, and was it confirmed as being the correct one for your vehicle? 
Issues occurred since the battery was changed by any chance? 
Kind regards,

Gareth. 

[Sarah86]

Hi Gareth,

I should have probably mentioned that before, its a yuasa HSB020. brand new from a motor factors.

The car was laid up some time because of a water damaged ECM and when this was solved at Audi we fitted the new battery. The car hasn't been coded to the new battery, could this cause issues?

 

Since then we've done about 400 trouble free miles, (apart from EM light with code P0471 exhaust pressure sensor) then the car has started cutting out with the 'esp fault' appearing on the dash each time. 

 

Kind regards, Sarah

[Magnet]

Thanks again Sarah,

I think that’s a very substantial battery, and if you go into Halford’s website, you should be able to put in your registration number and confirm whether it’s the correct one - which I would expect it to be. 
Does it need coding? Doubtful for that age of vehicle, but I could be wrong. 
New and Yuasa? Should certainly be serviceable, but I do recall a local mechanic (some years ago) not being too impressed with them, but should be OK now. 
Would I still get its efficiency checked at Halfords (and the alternator output)?
Yes I would, so you can eliminate it as being a culprit. 
Water damage? Possibly due to plenum chamber drain holes blocked - which I would expect Audi to have cleared. 
When the ESP light comes on, do you get an ABS light as well? 
Kind regards,

Gareth.