P0412AIR System Switching Valve A Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The switching valve is the electrically driven valve of this path – a solenoid valve, or on Pierburg/VW systems an electric changeover valve that applies vacuum to the pneumatic combination valve; valve A serves the first path or bank 1, valve B the second. P0412 is the general electrical fault in the control circuit of valve A, detected by comparing the driver's feedback with its commanded state. GM has used it since about 2015 specifically for an open circuit (200 kΩ or more, 20 of 25 samples, MIL after two trips) and reports shorts as P041F and P044F; older GM systems and Toyota use it for any driver fault. The valve then stays shut, so secondary air is missing and P0411 or P2441 may follow.
- What you may notice
- Check engine light on
- Secondary air inactive
- Secondary air readiness not set (emission test)
- Driving normal
- Likely causes
- LikelySwitching valve A faulty (coil open or shorted, water ingress)
- LikelyConnector corroded or wire open or chafed
- PossibleValve supply missing (fuse, main relay)
- RareDriver in the engine module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €40 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.