INDEPENDENT REFERENCE
P0401 — Exhaust gas recirculation flow insufficient detected
Generic powertrain DTC · MEDIUM priority for follow-up (not a certified safety rating)
What the code means
The EGR monitor sees less exhaust gas recirculation than commanded.
What you might notice
Check-engine light; possible pinging or elevated emissions.
Possible causes — not a diagnosis
Blocked passages; sticking EGR valve; vacuum/control failure; flow-sensor error.
Useful diagnostic checks
Inspect EGR passages and actuator command; verify the monitored flow response.
Next steps
Service blocked passages or failed controls after diagnosis.
Related OBD-II codes
These generic definitions are explanatory summaries of commonly standardized OBD-II powertrain conditions. Vehicle-specific code logic and service procedures must be verified against manufacturer documentation. EPA: On-board diagnostics.