P0412 Code: Secondary Air Injection (AIR) Switching Valve A Circuit Malfunction
🟠 Moderate severity · drivable
Drivable — this affects cold-start emissions, not drivability.
What P0412 means
The circuit for the secondary air injection switching valve A isn't working right. This valve opens to let the air pump push fresh air into the exhaust during cold start, helping the catalytic converter warm up faster.
Symptoms
- Check engine light is on
- Possible failed emissions test
- Possible air leak noise
- No driving symptoms
Common causes
- most common: Faulty switching valve or its solenoid
- common: Damaged wiring or connector
- less common: Blown fuse or faulty relay
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Check the fuse and relay for the AIR system | Yes | $0–60 |
| Replace the switching valve | Yes | $50–150 |
| Repair damaged valve wiring | Mechanic | $50–150 |
Frequently asked questions
Can I drive with a P0412 code?
Yes. It affects cold-start emissions, not drivability, but fix it before an emissions test.
What is the most common cause of P0412?
A faulty switching valve or its solenoid, or a wiring problem in the valve circuit.
How much does it cost to fix a P0412?
Typically $50–$150 for a new switching valve; a fuse or relay is cheaper.
Related codes
P0410
P0410 Code: Secondary Air Injection System Malfunction
P0413P0413 Code: Secondary Air Injection (AIR) Switching Valve A Circuit Open
P0414P0414 Code: Secondary Air Injection (AIR) Switching Valve A Circuit Shorted
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.