16795moderate severityPowertrain
Secondary Air Injection System
on 2003 Audi A6 3.0L V6 · AWD
What this code means
The secondary air injection system is not performing as expected (OBD P0411). This affects cold-start emissions and can trigger the check engine light.
Symptoms
- Check engine light
- Failed emissions test
- Rough cold idle
Common causes
- Faulty air pump
- Stuck combi/check valve
- Vacuum or hose leak
- Wiring fault
Diagnostic steps
- Read fault codes
- Test air pump operation
- Inspect valves and hoses
- Check electrical supply
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16515
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