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.
Affected components
- Secondary air pump
- Secondary air valve
- Secondary air passages
Common causes
- High likelihood: Air passages in cylinder head clogged with carbon
- Medium likelihood: Air pump weak
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.