Check Engine Code
P0401
Exhaust Gas Recirculation (EGR) Flow Insufficient Detected
What P0401 means
The EGR system routes a measured amount of exhaust back into the intake to lower combustion temperatures and reduce NOx emissions. P0401 means not enough flow is getting through — almost always carbon buildup in the EGR valve, passages, or DPFE sensor.
Vehicle-specific P0401 guides
P0401 can mean different things on different vehicles. Pick your make for engine-family specifics:
Symptoms
- Check engine light
- Engine pinging (knock) under load
- Slight power loss
- Rough idle
- Higher NOx emissions (emission test fail)
Likely causes (most common first)
- Carbon buildup in the EGR valve or passages (most common)
- Stuck or failed EGR valve
- Faulty DPFE sensor (Ford)
- Clogged EGR tube
- Vacuum supply issue on older vacuum-operated systems
Can I keep driving?
Medium — drivable but fix soon
Typical repair cost
DIY fixes can start near $30 (parts only). Shop repairs for P0401 typically run up to $500 depending on the underlying cause and vehicle. Start with the most common cause — Carbon buildup in the EGR valve or passages (most common) — before throwing parts at it.
Recommended parts & tools for P0401
Most common fix for P0401:
EGR / intake cleanerOur buyer’s guides cover the tools and parts that pair with AXLY:
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