Engine Light & Running Fan

**JonathanK** · 23-04-2018,05:42 PM

Hi Everyone,

I've been away for a week but before I went the engine light on my BiTdi came on for a couple of days. I left it in the garage for the week I was away in the hope that it would clear itself. I got it out of the garage today, the light was still on and when I parked it on the drive a minute later the fan was running and kept on running for quite a while.

I've noticed the fan running unnecessarily on a few occasions when the car has stopped but never had the engine light appear before. I'm assuming it's a sensor problem somewhere. Can anyone point me in the right direction and suggest what the problem might be?

Thanks

Jonathan

**A6S** · 23-04-2018,05:59 PM

The dpf is needing a regen.
When the fan keeps running after you park up then the regen didn’t finish.
This normally happens when the car is used for short trips.
Go for a long drive at high ish revs and it should clear. Beware that if you keep ignoring it there’s a point of no return and the dpf regen won’t work and will need replaced at a few grand.

**JonathanK** · 23-04-2018,06:05 PM

Thanks for that A6S. Is there anyway I can clear the engine light without VCDS?

**Rob69** · 23-04-2018,07:34 PM

If the engine light is on then there is a code logged and it will not clear itself, If you've been having frequent regens or fans running on and the EML light is on as opposed to the DPF light you need to get it scanned as you might have an EGR valve or cooler fault. Don't ignore it. You can clear the EML light and read codes with a cheaper OBDII scanner but diagnostics capability may be limited unless it is a better model.

**A6S** · 24-04-2018,10:17 AM

It will be worth getting a scan from any diag tool to see what the error is. Sooner rather than later. Audi parts like dpf or egr isn’t cheap if they break.
As said the better machines can do more than read and reset codes. The better ones can force a dpf regen rather than you driving about waiting for it to happen.

**JonathanK** · 24-04-2018,10:19 AM

Out of interest, how long does a regen take, either in time or miles? The car is booked in for diagnostic tomorrow.

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**ukgroucho** · 24-04-2018,10:35 AM

If I get home and the regen is happeningI'll take it back out (if I have time) and drive around in "sport" mode. Usually seems to take about 20 - 25 minutes and that is driving at speeds above 40 MPH.
I did read somewhere that regens only occur above 40 MPH - I don't think that is because of manifold temp, I suspect it's because they inject diesel into the exhaust to burn off the soot and you don't want to be doing that at low speeds in town etc.

With the BiTdi you can tell when it is doing the regen even when driving.
- In "D" mode you notice it holding lower gears even at 40 MPH. The exhaust note sounds a bit more sporty.
- At 60 MPH in "D" the BiTdi will still be in 7th gear under moderate throttle - normally it would shift to 8th at that point.
- If you have the lap timer enabled in VCDS then oil temp gives a clue. It will be significantly higher - so under normal driving where it might be in the 83C - 88C range you'll see it up at 93 - 94C

So I drive around in "S" to keep everything nice and hot and then after a while on a flat piece of road drive at 60MPH and put it in "D". If it drops into 8th then it is done.

**johnsimcox** · 24-04-2018,10:39 AM

Originally Posted by JonathanK

Out of interest, how long does a regen take, either in time or miles? The car is booked in for diagnostic tomorrow.

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I find a normal regen takes about 30 minutes, when I am aware it is happening which is usually in stop start traffic on my way to work and I see the idle speed is raised to about 1000rpm and the stop start does not activate. May take less time when making normal progree or on a motorway. It sounds like you need to do a forced regeneration and IIRC the manual suggests a trip of about 40 miles with highish engine revs

**A6@georgemac** · 25-04-2018,03:21 PM

I am learning a bit here - I have noted when coming home from a 50 mile drive, a lot of which is currently 40 - 50 MPH due to road improvements, the fan keeps running - which really surprises me - but now that explains it - just not clear why after that long drive the dpf regen is not finished.
I have only the 2.0 tdi manual, no engine warning lights - and I wish car manufacturers would let the driver know when the dpf regen starts and to drive at higher revs during this period - would perhaps save loads of grief with dpf's and EGR valves.
I am on my second Audi A6 diesel, and have had no bother with either of them, but my older diesel SAAB used to get a lot of grief with choked EGR valve.

Also makes it clear sometimes when I get to my destination the stop/start is blocked when I have a warm engine.

**johnsimcox** · 25-04-2018,04:12 PM

Originally Posted by A6@georgemac

just not clear why after that long drive the dpf regen is not finished.

Challenge is that the DPF may only have started a few minutes before you got home so it has not had the benefit of the full journey to do the regen. Only way to know if it is happening is that the idle rises to about 1000rpm from 800rpm and also the stop/start does not activiate and displays the crossed out "A" in the DIS (although that on its own is not necessarily evidence of a regen taking place)