P0412 Secondary Air Injection System Switching Valve A Circuit Malfunction

P0412 indicates a malfunction in Secondary Air Injection System Switching Valve A circuit. The controller detects an electrical problem in the valve A control path.

Code details

Generic OBD-II · P0

System: Emissions
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the air pump for P0412 until valve A circuit power, ground, control, and solenoid operation have been checked.

Symptoms of P0412

Check-engine light, often with no obvious change in how the car drives.
A failed emissions test or incomplete readiness monitors.
Sometimes a faint fuel-vapour smell (on EVAP codes).

Common causes of P0412

A worn catalytic converter or an oxygen/air-fuel sensor reading out of range.
EVAP leaks — a loose or failed gas cap, cracked hose, or purge/vent valve.
Exhaust leaks, fuel-trim problems, or a fault in a related monitor.

Useful checks before replacing parts

Check switching valve A command, control voltage, relay status, fuse feed, ground path, and freeze-frame conditions during secondary air operation.
Inspect valve A connector, wiring insulation, solenoid resistance, vacuum routing where used, water intrusion, and harness damage near heat sources.
Command the valve with a scan tool and confirm both electrical response and actual airflow routing.

Related OBD-II codes

These nearby emissions entries can help compare wording and pin down the fault area.