OBD-II code · generic

P0401

Exhaust Gas Recirculation Flow Insufficient Detected

System: EGR system
Severity: Moderate (3/5)
Can I keep driving?: Drive with caution

What does P0401 mean?

P0401 is defined as “Exhaust Gas Recirculation Flow Insufficient Detected”. This code indicates a problem with the exhaust gas recirculation (EGR) valve, the EGR cooler or their position/control circuits. EGR feeds part of the exhaust gas back into the intake to reduce NOx emissions.

Drive gently and only as far as you need to; have it checked as soon as possible.

Symptoms

Check engine light comes on
Shaking at idle, stumbling at low revs
Loss of power, and black smoke on diesels
On some cars, switching to limp mode

Common causes

Valve clogged with soot or stuck open/closed
EGR valve motor or position sensor failure
Problem with the EGR cooler bypass flap / vacuum line
Open circuit in the connector or wiring

How to diagnose it

Compare the requested and actual EGR position in live data.
Run an EGR actuator test with a diagnostic tool and watch the valve open and close fully.
Remove the valve and check for soot build-up.
On vacuum-operated systems, check the vacuum hoses and solenoid.

How to fix it

Clean a sooted valve and intake passage, and renew the gasket.
Replace a mechanically or electrically faulty valve and run the adaptation (learning) procedure.
Also fix the source of the soot (injectors, turbo, short trips); removing or disabling the EGR is not legal.

Manufacturer-specific meanings

The same code can mean something different on some makes.

Kia: Exhaust Gas Recirculation Flow Insufficient Detected

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This page is general information; an exact diagnosis needs measurements and a technician’s check.