Hi, wonder if anyone can help, just got an A4 Avant, high mileage but good condition and history. Have had the emission control light come on twice now in less than week of buying the car, dealer cleared fault yesterday but it's come back today. Have given it a good run at 3k revs yesterday to clear dpf. First time I've owned an Audi, so any advice welcome.

We had the same problem and it turned out to be the exhaust emission sensor I think their are 3 but diagnostics don’t tell you which one so trial and error I would get a diagnostics check did you get a warranty with the vehicle 

Ok thanks, dealer got mechanic to run diagnostic yesterday and came up with dpf regeneration, but this wasn't the warning light on the dashboard. Yes got extra warranty, thankfully. Just wondered if I'm ok to run the car while light on, is constant not flashing. 

The warning light covers numerous problems the dpf light might not come on if it’s not blocked it may need regenerating but the problem is exactly the same as mine we took ours to Audi Central just outside Birmingham and they sorted the problem and it was the sensor I have mentioned and our warranty covered it Audi Central are not a dealership but specialise in Audi VW and Skoda and they do all our work 

Ok great thanks, presume if light is constant I can still drive it? 

I would check that just in case where are you situated 

Certain garages can carry out a forced re gen  I think Halfords can do it 

Ok thanks, will leave it with dealer to sort to start with. New I may have some problems as you would expect with a car over 100k, but didn't expect warning lights in first week. Am I right in thinking this could be an ongoing issue, and is quite common with Audi diesels?

Dealer has now replaced dpf sensor, and put dpf cleaner in. Have given it good run out yesterday and made sure it had warmed up properly. Had it back for couple of hours, and light back on again with same dpf pressure error, so back to dealer. Been at dealers now for over 4 days overall, after buying less than 2wks ago, beginning to lose confidence in it. 

Edited May 7, 20233 yr by pa7206

Hello Pete,

Sorry to hear of your issue.

I think you will find you can now reject the car ( still within 30 days), since you have allowed the dealer 2 opportunities to repair it and they have failed. 
I would be taking good advice via. your local CAB, and make sure you record all the details and dates. 
Time is of the essence so you would need to move fairly fast, and with priority. 
Perhaps you could let us know how you get on.

Kind regards,

Gareth. 

I agree with Gareth. Sounds like the dealer is trying to avoid replacing the expensive dpf. I'd recommend rejecting the car. 

Thanks for the advice Gareth, Steve, much appreciated. I presume a new dpf will cost me £1000 plus? The car is really nice, just wasn't expecting these issues so quickly after buying it.

Hello Pete,

You are right in your belief that you should not be expecting these issues.

I think you have to make a decision (now?) whether you are going to reject it or not, before the dealer ‘plays you out of time’ on this. 
Probably a pessimistic view, but you may have found the reason why the the last owner sold it. 
Do you know how long the last owner had owned it? 
Kind regards,

Gareth. 

Yes, last owner for most of 8 years/100k use. Was main dealer history until about 4yrs ago, then independent garage. Last service history printout highlighted eml was on, so can't now be sensor as it's been changed. Am I right in thinking if there is a blockage or if there is a slight pressure leak to the pipes either going in our out of the dpf either side this can cause the eml to come on?

Easy in hindsight Pete, but shame you didn’t question the EML before buying. 
Apologies, but my earlier advice still applies. 
Kind regards,

Gareth. 

Hi Gareth, Steve, I've returned the car to the dealer now and have got a full refund from them. It came up with a crank sensor error also at start of week so decided enough was enough. A shame, as it was a nice car.