MasterTuning Fault code dictionary (DTC)

P0401 — EGR: insufficient recirculation flow

Severity: Warning Can you drive? Yes, no known limitation Make: All makes (OBD-II standard)
MeaningThe EGR valve is not recirculating enough exhaust gas. It is almost always a matter of dirt: the valve and its duct get coated with soot mixed with oil and no longer open fully.
FamilyPowertrain (P)

Typical symptoms

Engine warning light on
Slightly rough idle
Black smoke under acceleration
Hesitation when picking up

Common causes

Carboned or stuck EGR valve
Blocked recirculation duct
Clogged EGR cooler
Faulty electric actuator or vacuum unit

What to do

In most cases a thorough clean of the valve and duct solves it. On high-mileage engines with a mechanically seized valve, replacement is needed: check that it still moves before ordering the part.

Frequently asked questions

What does code P0401 mean?

EGR: insufficient recirculation flow. The EGR valve is not recirculating enough exhaust gas. It is almost always a matter of dirt: the valve and its duct get coated with soot mixed with oil and no longer open fully.

Can I keep driving with code P0401 active?

Yes, no known limitation

Common causes — P0401

Carboned or stuck EGR valve Blocked recirculation duct Clogged EGR cooler Faulty electric actuator or vacuum unit

How do you fix code P0401?

In most cases a thorough clean of the valve and duct solves it. On high-mileage engines with a mechanically seized valve, replacement is needed: check that it still moves before ordering the part.

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