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P0401: Exhaust Gas Recirculation Flow Insufficient Detected
Severity: Low Usually safe to keep driving, but get it checked.
What does P0401 mean?
The computer sees less EGR flow than it commanded. Carbon buildup is the most common cause.
Generic OBD-II definition: Exhaust Gas Recirculation Flow Insufficient Detected. Confirm applicability in your vehicle service information.
Common causes
- Carbon-clogged EGR passages
- Stuck or faulty EGR valve
- Faulty EGR position sensor or DPFE sensor
- Cracked vacuum lines (older vehicles)
Symptoms
- Engine pinging or knocking
- Possible emissions failure
Can I keep driving with P0401?
Severity: Low Usually safe to keep driving, but get it checked.
If the check engine light is flashing or the car runs badly, stop driving and have it checked.
Typical fixes
- Clean EGR valve and passages
- Test EGR valve
- Check the EGR feedback sensor