P0411
PowertrainEmission Controlsmoderate severitySecondary Air Injection System Incorrect Flow Detected
What P0411 Means
The secondary air injection system is not providing the expected airflow.
Symptoms
- Check Engine Light
- Failed emissions test
Common Causes
- Blocked AIR passages
- Stuck check valve
- Weak AIR pump
- Exhaust leak allowing backflow
Diagnostic Steps
- Monitor O2 sensor during AIR pump activation (should go lean)
- Check AIR pump output
- Inspect check valve
- Check for blocked passages
Where to start: Clear blockage or replace AIR pump/check valve.
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