P0412 — Secondary Air Injection System Incorrect Flow Detected
Drive with caution — fix soon.
What P0412 means
This code means the engine computer detected that the secondary air injection system isn't moving the right amount of air, which is the fresh air pumped into the exhaust at startup to cut emissions. It usually points to a faulty air pump, a stuck or leaking switching valve, or clogged passages and hoses. It's a fairly common code and is usually fixable without major engine work.
Common symptoms
- Check engine light is on
- Rough or unstable idle right after a cold start
- Buzzing or whirring noise from the air pump at startup
- Will likely fail an emissions test
- No noticeable change in everyday driving
Common causes
- Faulty secondary air injection pump
- Stuck, leaking, or clogged air switching valve
- Blocked or cracked air hoses and passages
- Carbon buildup restricting airflow in the system
- Wiring or electrical fault to the pump or valve
Typical repair cost
$200 – $700
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0412 code?
Usually yes, since the secondary air system mostly affects cold-start emissions and not everyday driveability. The car stays safe to drive, but it will likely fail an emissions test and run dirtier when cold, so plan to have it repaired.
How much does it cost to fix a P0412?
Most repairs run between about $200 and $700. Cleaning passages or replacing a switching valve is cheaper, while a new secondary air injection pump pushes the cost toward the higher end.
Is a P0412 code serious?
It's not a safety emergency and won't typically leave you stranded, but it does mean your emissions system isn't working properly. It should be repaired so the car passes emissions and doesn't pollute more than necessary.
What is the secondary air injection system in a P0412?
It's a pump and valve setup that pushes fresh air into the exhaust during cold starts to help the catalytic converter heat up and burn off pollutants faster. A P0412 means the computer detected the airflow wasn't what it expected.