P0401
EGR Flow Insufficient Detected
OBD-II
egr
What it means
Exhaust gas recirculation flow is lower than expected — clogged EGR passages/cooler or a stuck valve.
Seeing P0401?
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Run a free diagnosisRelated codes
SPN 411 / FMI 3
EGR Differential Pressure — Voltage High
egrMedium
SPN 412 / FMI 0
EGR Temperature — Above Normal (Most Severe)
egrHigh
P0402
EGR Flow Excessive Detected
egrMedium
P0403
EGR Control Circuit
egrMedium
General reference only — always confirm against the OEM procedure for your specific engine.