P0411 — Secondary Air Injection System Incorrect Flow
Drive with caution — fix soon.
What P0411 means
P0411 means the secondary air injection system, which pumps fresh air into the exhaust during cold starts to help the catalytic converter heat up and cut emissions, isn't flowing the correct amount of air. Common culprits are a stuck air switching valve, a failed air pump, or carbon and moisture clogging the system. It mainly affects cold-start emissions rather than everyday driving.
Common symptoms
- Check engine light is on
- Rough idle or rough running on a cold start
- Loud air pump noise or unusual whirring at startup
- Failed emissions test
- Little to no change in normal warm driving
Common causes
- Stuck or faulty air switching/control valve
- Failed secondary air injection pump
- Carbon or moisture buildup clogging the system
- Leaking or disconnected air hose
- Faulty check valve allowing exhaust back into the pump
- Wiring, fuse, or relay problems for the air pump
Typical repair cost
$150 – $600
Varies by vehicle and root cause.
Frequently asked questions
Can I drive with a P0411 code?
Usually yes. The secondary air system mostly works during cold starts, so the car typically drives normally when warm. You may notice rough running when cold, and it will fail emissions, so get it checked soon.
How much does it cost to fix a P0411?
It varies widely. A stuck valve clean or replacement can be $150-350, but a failed air pump is pricier, often $400-600 or more with parts and labor.
Is P0411 serious?
It's moderate. It won't usually leave you stranded and the engine generally runs fine warm, but it increases cold-start emissions and will fail a smog test, so it's worth repairing.
What causes incorrect secondary air flow?
The most frequent causes are a stuck air switching valve and a failed air pump, often due to carbon or moisture clogging the system. Leaking hoses and a bad check valve are also common.