A6 emissions control system warning - help!

[geoffd]

I have an A6 (2010) with a 2 litre diesel. Last night the emission control warning light came on. I drove home with no problems, it seemed to drive normally.

Is this something I have to worry about immediately?

Before I talk with Watford Audi, can anyone recommend an Audi specialist not too far from Ruislip?

Thanks,

Geoff

[944fan]

Probably the something with the DPF. It might need a regen. It could be the sensor. Worse case is the DPF is buggered.

What kind of driving do you do? Town or long distance?

You can try a regen yourself which involves driving at 45 mph + for 15-20 mins. Put all the ac and other stuff on to create load on the engine.

Mine came on a little while ago and eventually turned itself off. Not had a problem since.

[geoffd]

It's a mixture, but there is motorway and long distance driving. 240 miles on Friday, of which 70 was motorway. 100 miles on Saturday of which maybe 70 was motorway.

Geoff

[SteBrown91]

It's likely to be a sensor the CR engines were known to throw a dpf sensor occasionally, I think it's normally the first one before the DPF that goes. Is get it looked at though, as ignoring it could mean it won't regen and clog up

[VeeFource]

Often it's the EGR valve on the way out, especially if it throws the error when booting it. Doing motorway miles doesn't clean it out either which is a common misconception. Town driving and especially on supermarket fuel is what kills them and cumulatively so I'm afraid.

[jith]

VeeFource said:

Often it's the EGR valve on the way out, especially if it throws the error when booting it. Doing motorway miles doesn't clean it out either which is a common misconception. Town driving and especially on supermarket fuel is what kills them and cumulatively so I'm afraid.

This is an absolute myth.

Supermarket fuel is exactly the same as every other fuel and comes from the same source. I run my A6 2.4 petrol on Super unleaded from Tesco around the corner from my workshop. It is 99 octane, the highest you can buy anywhere. The car runs faultlessly at all times and pulls like a train.

Modern diesel cars are desperately flawed in design and are becoming more fragile as manufacturers attempt to bow to political pressures, particularly from the EU, to make these things run as clean as a petrol; something they will never achieve. I'm afraid it's just your luck what breaks next on your diesel car. The only part that is affected dramatically by town driving is the DPF; an appallingly unreliable piece of technology foisted upon the public due to poor research and development.

J

[geoffd]

Thanks for all your replies. The car is booked into Watford Audi next month. They thought it would be OK to keep driving.

Geoff

[Adrian E]

geoffd said:

Thanks for all your replies. The car is booked into Watford Audi next month. They thought it would be OK to keep driving.

Geoff

Be nice if they would read the fault codes to confirm it's nothing to worry about, before suggesting you keep driving it and potentially causing more expensive issues, just because they can't fit it in for several weeks....

As above if it's a DPF sensor and it doesn't recognise it needs to re-gen you could end up with a much bigger bill as a result.

Might be worth asking if they can do a quick fault code scan - if you were near me I'd offer to scan it, but I'm South of the M25

[VeeFource]

jith said:

VeeFource said:

Often it's the EGR valve on the way out, especially if it throws the error when booting it. Doing motorway miles doesn't clean it out either which is a common misconception. Town driving and especially on supermarket fuel is what kills them and cumulatively so I'm afraid.

This is an absolute myth.

Supermarket fuel is exactly the same as every other fuel and comes from the same source. I run my A6 2.4 petrol on Super unleaded from Tesco around the corner from my workshop. It is 99 octane, the highest you can buy anywhere. The car runs faultlessly at all times and pulls like a train.

My experience is based on extensive research and information given to me by a good friend that works as a senior process engineer in the industry. Your experience seems to be how well your petrol car is running from filling it up at Tescos around the corner. You also seem to have wrongly assumed that the RON is an absolute indicator to the quality of the fuel which is quite frankly laughable.

The reason supermarkets offer their fuel at lower rates is partly down to the reduced additive content. Tankers bound for their own branded stations use totally different fill stops at the refinery which contain many more engine protecting additives.

jith said:

The only part that is affected dramatically by town driving is the DPF; an appallingly unreliable piece of technology foisted upon the public due to poor research and development.

That is just absolute rubbish. The entire exhaust system up to the DPF can see soot build up from regular accelerations whilst not getting up to high enough temperatures to burn off as occurs during high speed driving. VNT systems can suffer particularly but the main issue with EGRs is that they're too far downstream in the system (as is the intake manifold which also cruds up) to have the soot burnt off. In fact EGRs are actually closed off completely under heavy acceleration and DPF regeneration which means they don't see the benefit of these high temperatures.

Avoiding supermarket fuel is a top recommendation for prolonging the life of your diesel engine and exhaust system, advise which can be easily found on most industry standard articles on the subject.

[jith]

VeeFource said:

jith said:

VeeFource said:

Often it's the EGR valve on the way out, especially if it throws the error when booting it. Doing motorway miles doesn't clean it out either which is a common misconception. Town driving and especially on supermarket fuel is what kills them and cumulatively so I'm afraid.

This is an absolute myth.

Supermarket fuel is exactly the same as every other fuel and comes from the same source. I run my A6 2.4 petrol on Super unleaded from Tesco around the corner from my workshop. It is 99 octane, the highest you can buy anywhere. The car runs faultlessly at all times and pulls like a train.

My experience is based on extensive research and information given to me by a good friend that works as a senior process engineer in the industry. Your experience seems to be how well your petrol car is running from filling it up at Tescos around the corner. You also seem to have wrongly assumed that the RON is an absolute indicator to the quality of the fuel which is quite frankly laughable.

The reason supermarkets offer their fuel at lower rates is partly down to the reduced additive content. Tankers bound for their own branded stations use totally different fill stops at the refinery which contain many more engine protecting additives.

jith said:

The only part that is affected dramatically by town driving is the DPF; an appallingly unreliable piece of technology foisted upon the public due to poor research and development.

That is just absolute rubbish. The entire exhaust system up to the DPF can see soot build up from regular accelerations whilst not getting up to high enough temperatures to burn off as occurs during high speed driving. VNT systems can suffer particularly but the main issue with EGRs is that they're too far downstream in the system (as is the intake manifold which also cruds up) to have the soot burnt off. In fact EGRs are actually closed off completely under heavy acceleration and DPF regeneration which means they don't see the benefit of these high temperatures.

Avoiding supermarket fuel is a top recommendation for prolonging the life of your diesel engine and exhaust system, advise which can be easily found on most industry standard articles on the subject.

Well, well, an expert, eh?

First off, let me assure you I don't talk rubbish. My experience is based on 45 years as a project design engineer, most of which was spent in the motor trade.

At no point did I imply that the octane rating of a fuel was a measure of the quality. What can be drawn from Tesco though is that they actually bother to market fuel at this octane rating; and believe me, it is patently superior to other fuels from local stations in this area.

I service some extremely expensive machinery, modern and old, and I experiment with fuels on my own vehicle and pass the benefits of this onto my customers. On Tesco 99 octane I get an improvement of around 5 MPG on my own Audi. It is a normally aspirated 2.4 30 valve engine.

On lesser octane fuels the knock sensors will retard the timing to the point where the drop in performance and economy is markedly noticeable, absolutely no question. If you are implying that Tesco would supply a petrol fuel of that quality, but the derv was of a poorer quality, I would state that you are way off the mark and completely mistaken, as is your "friend" that supplies you with this information.

In my experience bad fuel comes from poorly maintained stations, regardless of who owns them and what fuel they sell. In a modern diesel, dirt or water passing through the systems is absolutely fatal and will utterly ruin the injectors on a common rail system, most of which are in the region of £400 each. That kind of failure has nothing to do with the quality of the fuel, but everything to do with contamination.

An EGR valve on a modern diesel, (and petrol) engine is a component that requires regular maintenance regardless of what kind of driving the vehicle is subjected to. However, before we had common rail systems and DPFs they were far more reliable and long lived. Furthermore, many of the failures we see in this worshop are electronic in the control system and nothing to do with carbon contamination.

The modern engine is highly over-stressed and is becoming increasingly prone to failure, and when it does, the costs are positively ludicrous.

Now, I would appreciate you going off and insulting someone else: I have no time for it.

J

[VeeFource]

jith said:

Well, well, an expert, eh?

First off, let me assure you I don't talk rubbish. My experience is based on 45 years as a project design engineer, most of which was spent in the motor trade.

At no point did I imply that the octane rating of a fuel was a measure of the quality. What can be drawn from Tesco though is that they actually bother to market fuel at this octane rating; and believe me, it is patently superior to other fuels from local stations in this area.

I service some extremely expensive machinery, modern and old, and I experiment with fuels on my own vehicle and pass the benefits of this onto my customers. On Tesco 99 octane I get an improvement of around 5 MPG on my own Audi. It is a normally aspirated 2.4 30 valve engine.

On lesser octane fuels the knock sensors will retard the timing to the point where the drop in performance and economy is markedly noticeable, absolutely no question. If you are implying that Tesco would supply a petrol fuel of that quality, but the derv was of a poorer quality, I would state that you are way off the mark and completely mistaken, as is your "friend" that supplies you with this information.

In my experience bad fuel comes from poorly maintained stations, regardless of who owns them and what fuel they sell. In a modern diesel, dirt or water passing through the systems is absolutely fatal and will utterly ruin the injectors on a common rail system, most of which are in the region of £400 each. That kind of failure has nothing to do with the quality of the fuel, but everything to do with contamination.

An EGR valve on a modern diesel, (and petrol) engine is a component that requires regular maintenance regardless of what kind of driving the vehicle is subjected to. However, before we had common rail systems and DPFs they were far more reliable and long lived. Furthermore, many of the failures we see in this worshop are electronic in the control system and nothing to do with carbon contamination.

The modern engine is highly over-stressed and is becoming increasingly prone to failure, and when it does, the costs are positively ludicrous.

Now, I would appreciate you going off and insulting someone else: I have no time for it.

J

I’m not intending to insult you, but when someone accuses my statement as being a myth when backed up with nothing more than the limited experience of running their own car then you really shouldn’t be surprised if this is met with contention.

I also work as a design engineer and always on projects which is usually a given. I’m not picking at your title, just can’t say I’ve ever come accross a project design engineer before. I can only assume this is more withdrawn from the technical towards the project management side of things?

Anyway, I’d sooner take the word of someone whom has significant experience of designing the equipment to manufacture the fuel than from a customer of their product.
I’ve no idea how you interpreted my remark as implying tesco derv is inferior to tesco super, my point was that RON is no indication of the quality or quantity of additives going into the fuel to produce a cleaner burn. Just because a higher octane fuel burns more quickly doesn’t mean you’re going to get a cleaner burn with less soot build up which is the whole point of this conversation, not how efficient or how much power the engine is producing.

Given fuel is stored in vast tanks underground at all stations, the only real way the fuel can be adversely effected is cross contamination between fuels, but even then this would be incredibly rare. So if you’re suggesting the way the fuel sits in a tank between stations is more important than the quality of the fuel you put into them in the first place then I really fear for your technical expertise.

If as you say an EGR is a component requiring regular maintenance, why is it not in any of the service schedules? And why is it mounted on the back of the OPs engine with a 4 hour book time to remove and refit? I think I’ll stick with the better quality fuel option thanks all the same.

So are you saying most of the DPF, EGR and VNT related issues reported are due to a fault in the control system of the component rather than a mechanical issue within the component itself? Well that’s a lot of very consistent electrical faults in which case wouldn’t you say?