Passage EGR restreint

The ports carrying recirculated gas — through the head, the manifold or the cooler — narrowed by hard deposits. This is distinct from a stuck valve and the distinction decides the repair: the valve can be perfect, moving freely through its full range, while almost nothing flows through the passage behind it.

Which is why a new EGR valve so often fails to fix a flow code. The module opens the valve fully, sees the flow still short, and sets the same fault within days.

It is the usual explanation for a closed-loop EGR flow code at its limit, because a correction running out of authority means a restriction larger than the control can compensate for — and only a physical blockage does that.

Repair is labour rather than parts. The passages have to be opened and cleaned mechanically; chemical cleaners poured through rarely shift deposits that have baked for years, and on some engines the intake manifold must come off to reach them. A quote weighted heavily toward labour is honest here.

Check the intake throttle at the same time. On a diesel it creates the pressure difference EGR needs to flow at all, and a coked one produces low flow with a clear passage.