What does P0412 mean?
The secondary air injection system pumps fresh air into the exhaust for the first minute or two after a cold start. That helps the catalytic converter warm up faster.
The computer tried to control the part and saw an electrical fault, usually an open circuit.
Codes are a starting point. They tell you which test failed, not which part to replace. Check for other stored codes and fix those in a sensible order.
Symptoms
- Check engine light
- Loud whine or no sound from the air pump on cold start
- Failed emissions test
Common causes
- Open circuit in the solenoid or its wiring
- Unplugged or corroded connector
- Blown fuse feeding the component
- Failed component
How to diagnose P0412
- Check the fuse that feeds the component.
- Measure the component's resistance and compare it with the service spec.
- Check for power at the connector with the key on, and for a broken control wire back to the computer.
- Listen for the air pump right after a cold start.
- Check the fuse and relay.
How to fix it
- Replace fuse or relay
- Replace the check/combination valve
- Replace the air pump
Estimated repair cost
Likely repairs for P0412 run from about $200 to $1,200, depending on the cause.
| Repair | Typical range (parts + labor) |
|---|---|
| Diagnostic fee (scan + testing) | $100 - $200 |
| Secondary air check/combination valve | $200 - $600 |
| Secondary air injection pump | $400 - $1,200 |
These are rough US estimates for an independent shop in 2026, based on typical parts prices and standard labor times. Dealers, big trucks, luxury brands and high-cost areas often run higher. They are not quotes. Use the repair cost estimator to adjust for your vehicle.
How serious is P0412?
Low severity
Safe to drive. It mainly affects cold-start emissions.
P0412 FAQ
What does P0412 mean?
P0412 stands for "Secondary Air Injection System Switching Valve "A" Circuit". The secondary air injection system pumps fresh air into the exhaust for the first minute or two after a cold start.
Can I drive with a P0412 code?
Safe to drive. It mainly affects cold-start emissions.
How much does it cost to fix P0412?
It depends on the cause. The likely repairs for P0412 range from about $200 to $1,200 at an independent shop in the US, plus a diagnostic fee of roughly $100-$200. These are rough estimates; dealer prices and some vehicles run higher.
What is the most common cause of P0412?
The most common causes are: open circuit in the solenoid or its wiring; unplugged or corroded connector; blown fuse feeding the component.