I have an Audi A4 2.0 tdi technik. A short while ago it came up with P04010 EGR insufficient flow detected error. We have cleaned the pipe from the block to inlet manifold (dirty but not blocked) and replaced the whole EGR/cooler unit (EGR valve, vacuum actuator and sensor all come as one unit) - the old cooler was blocked solid so the error code made sense.

we cleared the error code after replacing the unit but it keeps returning. Sometimes, but not always, it triggers the engine management light.

any ideas please?

A further update, we have checked right into the inlet manifold where the egr feeds back in and also the tube where it passes through the back of the block are completely clear.

we tried fitting the electric unit with the position sensor off the old one (that was working but the body was blocked) but that caused a constant hunting and a P0403 fault immediately so has been taken back off. 
The EGR flow is varying with throttle as you drive along as you would expect.

at idle it is around 22kg/hr, it goes into the 60-70’s as you accelerate. Taking your foot off the throttle quite quickly seems to be what triggers it, the flow drops momentarily to 0.2-0.3 kg/hr. 

Problem solved, mechanical issue with new valve. Bolted old valve and body to new cooler and fault gone. Pity you cannot just buy the cooler

Glad to read you have solved it. EGR valve blockages are a common problem.

On 8/30/2025 at 1:15 PM, Kath said:

Problem solved, mechanical issue with new valve. Bolted old valve and body to new cooler and fault gone. Pity you cannot just buy the cooler

Kath, Apologies for thread necrosis, however, I'm banging my head on the wall over a 2016 B8.5 (engine code DEUA - so appreciate I might be comparing apples with oranges) with the same fault code - quoted £2.6k by a local garage/DPF specialist for replacement of which £1.5k is labour ("engine out job, mate"). Together with known extra work for a DMF replacement, 93k on the DPF and the inevitable timing belt it's uneconomical for me to push it through a garage...I'm just trying to drag the car a little further before scrapping it. You (OP) suggest (or I've interpreted) that you did much of the work yourself - is this true and if so just how difficult a job is it and how long did it take you? Any online resources that you found that were useful?  

Yes we replaced the EGR (valve plus cooler) ourselves (CJCB 2013 2.0tdi engine). It took about a day to remove and replace and you need to be double jointed for a couple of the bolts but if you are able to do it much better than a 4figure garage bill. Certainly on my engine you did not need engine out.
An aftermarket EGR was about £360. It’s the cooler which is the issue, it becomes blocked solid, but you cannot buy that in its own. 
Also what indicates you need a new DPF? I was getting the flashing glow plug light when it tried to regenerate but this was actually a turbo pressure fault triggered by back pressure from the blocked EGR. I still get it very occasionally but it immediately resets and the car now has over 190k miles on the original DPF. 

Kath, thanks for the reply. Although I can squint into the engine bay and compare that against some online B9 workshop manuals it's still very difficult for me to observe the routing of the EGR cooler pipe and where the pipes are routed - so knowing that yes, it's feasible to DIY. Double jointed wrists, though - that's a young man's game. 

I was of the thought of a lot of YouTubers that I've been watching that removal/cleaning/assessming the EGR would be the best first step, but realise that much of the cost/effort is in the labour. But if it was just the cooler or the valve then an ultrasonic tank filled with some interesting fluid would be my first call. I wouldn't baulk at a replacement valve but as you say the EGR/Cooler is a single part from the factors (and from the quote I've got is somewhere between 'whoah' and 'eek' (still less than a grand and if that bought me another year on the car I'd be happy).

DPF?, Just because internet wisdom for P0401s suggested the DPF, together with the age/mileage - it's where I started. I'm moving away from that diagnosis (perhaps the Internet isn't always right?) having talked this through with an Audi buff (with a 2 post lift) - it was originally the reason I took it to a DPF specialist but they ran it around the block, pulled the codes, quoted for EGR, and helped me lose 150 pounds from my back pocket within the space of an early morning. I am getting frequent regens but I need to isolate that from this EGR issue, I think, I've never seen a DPF fault code. I am now running with DPF/EGR snake oil in the fuel tank, and of note all this started shortly after I resigned/retired from work and my mileage dropped to single-figures daily - coincidence?

Quite likely linked. Diesels do not like short trips. A regular good thrash down a road (sorry officer a bit of spirited driving) will help but a regen every few hundred miles is not surprising with a few miles each day. 

1 hour ago, Doddy said:

Kath, thanks for the reply. Although I can squint into the engine bay and compare that against some online B9 workshop manuals it's still very difficult for me to observe the routing of the EGR cooler pipe and where the pipes are routed - so knowing that yes, it's feasible to DIY. Double jointed wrists, though - that's a young man's game. 

I was of the thought of a lot of YouTubers that I've been watching that removal/cleaning/assessming the EGR would be the best first step, but realise that much of the cost/effort is in the labour. But if it was just the cooler or the valve then an ultrasonic tank filled with some interesting fluid would be my first call. I wouldn't baulk at a replacement valve but as you say the EGR/Cooler is a single part from the factors (and from the quote I've got is somewhere between 'whoah' and 'eek' (still less than a grand and if that bought me another year on the car I'd be happy).

DPF?, Just because internet wisdom for P0401s suggested the DPF, together with the age/mileage - it's where I started. I'm moving away from that diagnosis (perhaps the Internet isn't always right?) having talked this through with an Audi buff (with a 2 post lift) - it was originally the reason I took it to a DPF specialist but they ran it around the block, pulled the codes, quoted for EGR, and helped me lose 150 pounds from my back pocket within the space of an early morning. I am getting frequent regens but I need to isolate that from this EGR issue, I think, I've never seen a DPF fault code. I am now running with DPF/EGR snake oil in the fuel tank, and of note all this started shortly after I resigned/retired from work and my mileage dropped to single-figures daily - coincidence?

Hi your DPF and EGR are completely different on your model as the EGR cooler lives in the DPF, its a really bad design doomed to fail so they were not far out with the price to replace as you have to remove all the front of the car to get the DPF out its about twelve hours whichever way you do it, then factor in the DMF and clutch thats another couple of grand, if I were you I would sell it to whoever wants it the most and go buy something petrol and Japanese I guarantee it will outlast you.

Steve.

1 hour ago, Stevey Y said:

Hi your DPF and EGR are completely different on your model as the EGR cooler lives in the DPF, its a really bad design doomed to fail so they were not far out with the price to replace as you have to remove all the front of the car to get the DPF out its about twelve hours whichever way you do it, then factor in the DMF and clutch thats another couple of grand, if I were you I would sell it to whoever wants it the most and go buy something petrol and Japanese I guarantee it will outlast you.

Steve.

Steve, you're pretty much paraphrasing my thoughts. I was watching a video of an A6/B9 with the EGR on the underside of the engine - I thought separate but lower than the DPF (and turbo - closer to rear of engine bay) - either way a complete mare to get to and explains some of the information of removing the wheel/driveshaft to get to it. Petrol and Japanese?, again, exactly where my thoughts were heading. Thanks for your view - genuinely appreciated - it feeds the devil on one shoulder whilst eternal hope feeds the devil of the other shoulder to repair. If I'm being honest I think you're right, though. A shame because I have enjoyed this car, but...

1 hour ago, Doddy said:

Steve, you're pretty much paraphrasing my thoughts. I was watching a video of an A6/B9 with the EGR on the underside of the engine - I thought separate but lower than the DPF (and turbo - closer to rear of engine bay) - either way a complete mare to get to and explains some of the information of removing the wheel/driveshaft to get to it. Petrol and Japanese?, again, exactly where my thoughts were heading. Thanks for your view - genuinely appreciated - it feeds the devil on one shoulder whilst eternal hope feeds the devil of the other shoulder to repair. If I'm being honest I think you're right, though. A shame because I have enjoyed this car, but...

Hi they are a great drive but having owned the A6 2.0 [same  engine] which I ran up to over 270k as a cab I can assure you that car could well be the decimation of your finances if you let it, I can thoroughly endorse a Honda Jazz the later versions are well equipped but the main feature is the engine which if kept well is bullet proof, consumables such as brakes tyres etc are better than reasonable and at around fifty to the gallon they won't disappoint.

Steve.