Trouble code
P0411
Secondary Air Injection System Incorrect Flow
What P0411 means
The secondary air system, which pumps air into the exhaust on cold start to help the catalyst light off, is not flowing correctly.
Symptoms you may notice
- Check engine light
- Loud pump noise on cold start
- Failed emissions test
Common causes, cheapest first
- Failed secondary air pump
- Blocked air injection passages
- Failed check valve
- Leaking or disconnected hose
Before you buy anythingCarbon blocks the injection ports on many engines. Confirm the passages are clear before fitting a new pump, or the new pump will fail the same way.
What to do next
- Confirm the code with your own scan tool, or have it read free at a chain parts store.
- Decode your VIN so you know your exact engine and build date.
- Work down the causes above from cheapest to most expensive.
- Search NHTSA for a recall or service bulletin covering this symptom on your vehicle.
- Read the engine buying guide before ordering.
P0411 is a generic OBD-II code, standardized across every make and model sold in the US from 1996 onward. The meaning is the same on any vehicle; the specific part and its location are not.
Parts
Parts commonly needed for P0411
These go to Amazon. We earn a commission if you buy, at no extra cost to you — see our affiliate disclosure. Which one you actually need depends on diagnosis — read the note above first.
Confirm fitment against your VIN on the listing page before ordering. A part that matches your year and model can still be wrong for your build date or engine code.