گرفتگی مسیرهای EGR

The drilled and cast passages carrying exhaust gas from the manifold to the intake, blocked with the soot and oil residue they were always going to accumulate. The valve gets replaced and the passages do not get cleaned, which is the single most common reason an exhaust gas recirculation fault returns within weeks of a repair.

A blocked passage and a stuck valve produce the same code — commanded flow not achieved — and the module cannot distinguish them, because it sees position feedback from the valve and a resulting change in manifold conditions. A valve that moves correctly through its full travel while flow codes persist is the signature of a blocked passage.

Diesel engines and short journeys make it worse, because cooler exhaust deposits more and never bakes it off. Inspect the passages with the valve removed rather than assuming, and clean back to the manifold face; the restriction is often at the far end where nobody looks. A cooler in the circuit blocks the same way and is the part most likely to be missed, since it is downstream of everything that gets cleaned.