Exhaust gas recirculation flow insufficient

The EGR monitor measured less flow than expected during a test; it does not name the failed part.

WHAT IT GENERALLY REPORTS

A starting point, not a parts list.

The vehicle’s exhaust-gas-recirculation monitor detected less flow than expected under its test conditions. A code can result from a flow, control, or feedback issue; it is not a part-replacement instruction.

Common symptoms

The check-engine light may appear without a clear driveability change.
Some vehicles may idle unevenly, hesitate, or feel less responsive.
Symptoms depend on how the vehicle controls and monitors EGR flow.

Possible causes

A restricted EGR flow path or a valve that does not behave as expected.
A control, feedback, or sensor condition affecting the monitor result.
A related engine or exhaust condition that needs vehicle-specific diagnosis.

Safe initial checks

Record P0401 with related codes and any scan-tool snapshot data.
Note any change in idle or response and when it happens.
Do not remove emissions components or touch hot exhaust hardware; keep the diagnosis to observation and saved information.

When to get professional help

A technician can check commanded operation and measured response using information for the exact vehicle.
Seek help sooner if the vehicle stalls, loses power, or becomes unsafe to operate.