P0412: Secondary air switching valve A circuit malfunction
The ECU has found an electrical fault in the circuit of the valve that lets secondary air into the exhaust. Usually the connector, wiring or valve.
| Code | P0412 |
|---|---|
| System | Engine and transmission |
| Group | P04xx, Emissions control |
| Type | Generic: it means the same on every make |
| Can you keep driving? | Yes, no rush |
What P0412 means
Switching valve A opens the path for secondary air to reach the exhaust while the pump is running. The ECU controls it electrically and has seen that its circuit is not responding properly (broken wire, short or damaged coil). Which valve is A is defined by each manufacturer.
Most common causes
- Loose or corroded valve connector
- Broken or chafed wiring
- Failed valve coil
- Fuse or power supply to the circuit
- ECU fault (rare)
Symptoms
- Engine warning light on
- Secondary air stops working
- Failing an emissions test
- Usually no change in how the car drives
Can you drive with P0412?
Yes, no rush It does not affect normal driving. You can keep using the car and fix it when convenient, before the next inspection.
How to check it
Find the valve (usually next to the secondary air hoses) and check that its connector is firmly seated and clean. A garage can measure the coil resistance and operate it with their diagnostic tool.
How to read and clear P0412 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0412 with this same explanation and whether it’s confirmed, pending or permanent.
With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.
Similar codes
- P0408 EGR sensor B circuit high
- P0409 EGR sensor A circuit malfunction
- P0410 Secondary air injection system malfunction
- P0411 Secondary air injection incorrect flow detected
- P0418 Secondary air injection relay A circuit malfunction
- P0420 Catalytic converter efficiency below threshold (bank 1)
- P0421 Warm up catalyst efficiency below threshold (bank 1)
- P0430 Catalytic converter efficiency below threshold (bank 2)
- P0400 Exhaust gas recirculation (EGR) flow malfunction
- P0401 Exhaust gas recirculation (EGR) flow insufficient
- P0402 Exhaust gas recirculation (EGR) flow excessive
- P0403 EGR control circuit malfunction
P0412 is a generic code, so it means the same on any make, for example on Alfa Romeo, Audi, Dacia, Kia, Opel / Vauxhall, Toyota. See what Final OBD does on your car in makes and models.
What does code P0412 mean?
Switching valve A opens the path for secondary air to reach the exhaust while the pump is running. The ECU controls it electrically and has seen that its circuit is not responding properly (broken wire, short or damaged coil). Which valve is A is defined by each manufacturer.
Can you drive with P0412?
It does not affect normal driving. You can keep using the car and fix it when convenient, before the next inspection.
How do you clear P0412?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0412 comes back.
Read it on your car
Final OBD reads the faults of every control unit for free, including each make’s own codes, and with Pro explains each one in plain English. Free clears engine faults at no cost.
Coming soon
Mid to late October 2026
If you want to try it in your car before anyone else, send us your email and we will add you as a tester.
info@finalobd.com