P0411
Secondary Air Injection System Incorrect Flow
When the ECU commands secondary air injection, the actual flow measured by the front oxygen sensor (or a dedicated mass flow meter) does not match the expected value. Usually a partially blocked passage or a leaking combi valve.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Air passages in cylinder head clogged with carbonCommon
- Air pump weakPossible
Parts involved
- Secondary Air Pump
- Secondary Air Valve
- Secondary Air Passages
P0411 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.