P0401 EGR insufficient flow detected

[CupraDine]

So I have the code P0401 logged in my ecu, which is EGR insufficient flow detected, on my A6 with a CDYA engine. The code is down as intermittent which is why I think the EML hasn't come on yet.

My question is, where do I start with this? I have read about engine cleaning (terra/hydro cleans) along with things like seafoam. Also checking a few of the ports as these can block, most common it seems are the ports just behind the throttle body on the intake.

Any help would be appreciated, trying to sort this before it throws a light or does permanent damage.

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[pelhamsdetailing]

You're likely to have a blockage at or around where the EGR joins with the throttle body, as that's where the exhaust gas meets with air and minor amounts of oil and fumes via the crank case system. I would personally start there and see how bad it is. If it's coked up, then that's likely what's causing an insufficient amount of flow to be allowed through. If it's done over 100k with the EGR functioning, there will definitely be some form of build up within upper and lower air intake system (the Y shape part after the throttle body going towards the swirl flaps), as well as the swirl flaps. The EGR system will likely see some build up too. If you feel confident and capable, you'll need to take the bits off to clean them most effectively.

Be mindful of any fuel lines you need to take out to remove parts of the upper and lower intake system, as this system needs to be primed via VCDS after being refitted before starting the engine. A CAPA engine is the only engine I know that does not need this performed.