Hi all,

Ploughed the forums but can't quite find answer I'm after. Am getting P0401 egr insufficient flow using a handheld fault reader. Have just replaced intake manifold flap assembly (which sorted that particular issue) and cleaned out the egr valve in the process. Was hoping that the clean out would prevent code returning but it hasn't. When I had the egr valve off I could move it by pushing on the valve with a piece of wood. Moved freely, no sticking but took a fair amount of force to counteract the spring return (this may be normal, I've got nothing to compare to!)

I have checked hose to n18 valve block by removing each end and sucking on one whilst blocking the other. Not the best test, I know, but enought to check for major leaks. Seemed airtight. Also cleaned some crud from around where the hose enters the valve block. Reassembled everything.

With engine running I removed hose from egr valve and I am getting vacuum there. Again, I don't have the right tools so only checked by placing finger over the end! Vacuum doesn't seem to vary with revs and is enough to tug gently on the skin.

Attached a spare bit of hose to the egr valve and I can't blow on it at all, but can suck a constant stream of air from it without ever seeming to meet an increase in resistance. Could this mean that the diaphragm has failed in the valve?

Other things I've read about are failed MAF sensors (as this is what is used to deduce reduced flow through egr valve-if airflow from air box doesn't reduce, it means the egr isn't contributing to the overall gas volume being drawn into the manifold). I don't know how to test for this though.

Any ideas about what the most likely culprit for this code could be? The car drives fine and I get 60mpg doing mainly motorway miles to work. I do get the over boost code and limp mode fairly regularly, but assume this is an unrelated problem from what I've read.

Cheers

Sounds like the diaphragm has failed in the valve. Can you borrow a mityvac pump, and try to build a vacuum.