P0401Severity: Medium
P0401 – EGR Insufficient Flow
Exhaust gas recirculation (EGR) flow is insufficient.
What it means
The EGR system routes some exhaust gas back into the intake to lower combustion temperature and NOx. Insufficient flow usually means carbon buildup.
Symptoms
- Knock/ping
- Failed NOx emissions
- Idle issues
- Check-engine light
Common causes
- Carbon clogging (EGR valve/passages)
- Faulty EGR valve
- Faulty DPFE/pressure sensor
- Blocked vacuum line
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Frequently asked questions
What does trouble code P0401 mean?
P0401 – EGR Insufficient Flow. The EGR system routes some exhaust gas back into the intake to lower combustion temperature and NOx. Insufficient flow usually means carbon buildup.
Can I drive with a P0401 code?
You can usually drive short distances, but it's best to have it checked before it gets worse.