What Does P0412 Mean?
The ECM has detected an electrical malfunction in the Secondary Air Injection (AIR) switching valve A circuit. The switching valve directs secondary air to the correct exhaust bank or switches between AIR delivery modes. This code indicates a circuit-level fault — open, short, or high resistance — in the solenoid or relay that controls this valve. The driver will typically not notice any symptoms during normal driving.
Common Causes
30%
Failed AIR switching valve solenoid — open or shorted coil winding
25%
Wiring damage — open or short in the switching valve control circuit
20%
Corroded or damaged connector at the switching valve
15%
Failed relay or fuse in the AIR system power supply circuit
10%
ECM driver circuit failure for the switching valve output
Diagnostic Steps
1
Locate the AIR switching valve A and disconnect the electrical connector. Measure the solenoid coil resistance — compare to spec (typically 20–60 ohms). Open (OL) or very low resistance indicates a failed solenoid.
2
Check for battery voltage at the power pin of the connector with key on — if missing, trace the power supply circuit through the relay and fuse.
3
Verify the ECM is providing a ground-side control signal by backprobing the control wire and commanding the valve using bidirectional scan tool control.
4
Inspect the connector and wiring for damage — the switching valve is typically located in the engine bay where heat, moisture, and vibration can damage connections.
5
If the solenoid and wiring check good, command the valve on/off while listening for a click — a mechanically stuck valve may have good electrical readings but still fail to operate.
Estimated Repair Cost
$100 - $400
Parts + labor, varies by vehicle and location
The ECM has detected an electrical malfunction in the Secondary Air Injection (AIR) switching valve A circuit. The switching valve directs secondary air to the correct exhaust bank or switches between AIR delivery modes. This code indicates a circuit-level fault — open, short, or high resistance — i...
The most common cause of P0412 (Secondary Air Injection System Switching Valve A Circuit Malfunction) is: Failed AIR switching valve solenoid — open or shorted coil winding
Typical repair costs for P0412 range from $100 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. The AIR switching valve is part of the cold-start emissions system and does not affect engine performance during normal operation. The vehicle will fail emissions testing. No safety risks.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0412 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control / Secondary Air Injection
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
