P04DA

Closed Loop EGR Control At Limit Flow Too High

Same as P04D9 with the controller fully closing the actuator yet still measuring more EGR flow than required. The valve does not seat fully, or position feedback under-reads.

Check engine light: Yes
Emissions related: Yes
Repair difficulty: medium

Symptoms

Check engine light on
Pinging or knocking under load
Power loss and hesitation
Possible rough idle
Failed emissions inspection (NOx)

Common causes

Ordered by how often each turns out to be the cause.

Valve does not seat fully (debris or wear)Common
Position sensor offsetPossible

Parts involved

EGR Valve A
EGR Position Sensor A

P04DA is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.