What it means
Secondary Air Injection System Switching Valve A Circuit: an electrical fault is present in the circuit.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The AIR switching valve A directs secondary air into the exhaust during the cold-start emissions routine. The ECU monitors the electrical circuit that operates this valve. P0412 sets when it detects an electrical fault in the valve A circuit, without specifying whether the fault is an open or a short.
Common causes
Most likely first.
- Switching valve A solenoid failure
- Open or shorted wiring in the valve circuit
- Loose, damaged, or corroded connector
- Control module driver fault
Symptoms
- Check engine light on
- Failed emissions inspection
- Possible roughness during cold start
How to diagnose it
- Check freeze-frame data and related AIR codes to see when the valve A circuit fault occurred and whether other circuit faults are present.
- Locate switching valve A using vehicle service information, then inspect its connector and nearby wiring for corrosion, looseness, chafing, or heat damage.
- Check the valve A solenoid for an open or short using the manufacturer's test procedure and specification.
- Test the valve A circuit for continuity and shorts to power or ground, following the wiring diagram.
- If the valve and wiring pass, verify the ECU control and power circuits before considering an ECU driver fault.
Common fixes
- Clean and secure a loose or corroded valve A connector.
- Repair damaged or chafed wiring in the valve A circuit.
- Replace the switching valve A solenoid if it fails its electrical test.
- Repair the ECU driver circuit only after confirming the valve, wiring, and power supply are sound.
Can I keep driving?
This fault usually does not prevent normal driving, but the AIR cold-start emissions function may not work and the vehicle may fail an emissions inspection. If cold-start roughness develops, limit unnecessary short trips until the valve A circuit is repaired.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.