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.
Low severity. Can I keep driving?Yes, you can keep driving, though it should be repaired: the car pollutes more at startup and may not pass an inspection.
Symptoms
- Check engine light on
- Secondary air inactive
- Secondary air readiness not set (emission test)
- Driving normal
Most likely causes
- Switching valve A faulty (coil open or shorted, water ingress)
- Connector corroded or wire open or chafed
- Valve supply missing (fuse, main relay)
- Driver in the engine module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: easy
- It affects emissions.
What each character of P0412 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 4: Emissions
- 12: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0412?
Yes, you can keep driving, though it should be repaired: the car pollutes more at startup and may not pass an inspection.
What causes code P0412?
The most common causes are: switching valve A faulty (coil open or shorted, water ingress); connector corroded or wire open or chafed; valve supply missing (fuse, main relay).
Related codes
- P0413AIR System Switching Valve A Circuit Open
- P0414AIR System Switching Valve A Circuit Shorted
- P0415AIR System Switching Valve B Circuit
- P0411AIR System A Incorrect Flow Detected
- P2440AIR System Switching Valve Stuck Open (Bank 1)
- P2441AIR System Switching Valve Stuck Closed (Bank 1)
Sources
- gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
- gsi.ext.gm.com: 2006file4
- static.nhtsa.gov: SB 10061665 2280
- techtips.ie: obd and secondary air system finding and remedying
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.