P0401 EGR insufficient flow

[passatwoes]

Hi everyone new member.
This concerns a 2007 2.0 TDI diesel PD engine passat.
Warning light on dash. Got a code reader and it says P0401 EGR insufficent flow detected.
Took the EGR off cleaned it, and took the plastic cover off the back and mechanically it works fine all gear wheels go round and the little valve opens and closes just fine.
Re-fitted last night. Cleared the warning light, started the car and the warning light came on again. Engine runs fine. No mis-fire or lumpyness.

Question is this: Is the EGR electronically fault. Should i buy a new EGR valve ? Or might it be something else that might be causing the fault ??
Any help most appreciated.

Paasatwoes

[Radio89]

The pipes in the EGR system can get clogged up with carbon too, not just the valve, thus restricting flow. If possible remove the pipes and give them a good scrub.

[martin1810]

The ecu does not measure egr flow. It measures MAF sensor flow. The ecu interprets MAF value too high as being egr flow too low and sets code p0401. Most of the time this is correct and the egr needs replacing.