P0411: OBD-II code P0411 means the secondary air injection pump isn't delivering the airflow the PCM commanded — cold-start emissions can't be cleaned up quickly.

Symptoms

• Check engine light is on; the engine drives normally but may have a longer cold-start emissions warmup.
• No power or drivability symptoms — the fault typically only shows up in emissions tests and the CEL.
• You may hear the air pump running noisily at cold start, or hear nothing at all when it should be running.

Common causes

• A failed secondary air injection pump — commonly seized or with worn brushes on high-mileage vehicles.
• A blocked or corroded air injection hose, one-way check valve, or manifold passage restricting airflow.
• A stuck-closed control solenoid or a failed vacuum switching valve preventing pump activation.

What to do?

Command the secondary air pump on with a scan tool at cold start — listen for it running. Inspect hoses and check valves for rust and blockage. Test pump current draw with an amp clamp. Replace the pump if it's seized; clear passages and replace check valves if blocked. This is often a mechanical, not electrical, fault.