P0412Powertrain
Powertrain · SAE
Secondary Air Injection Switching Valve A Circuit Malfunction
Meaning
The ECM has detected a general electrical fault in the circuit of secondary air injection switching valve A. The valve, controlled by the ECM via solenoid, is not responding correctly to the control signal.
Common causes
- Oxidised, loose, or damaged electrical connector at the switching valve
- Open or shorted solenoid winding in the valve
- Damaged wiring between ECM and valve, shorted to ground or supply voltage
- Mechanically seized switching valve
- Faulty internal driver output in the ECM
Symptoms
- MIL light on, DTC P0412 stored
- Secondary air injection system inoperative
- Elevated emissions during engine warm-up
- Possible slow catalyst light-off during cold start
- No operational noise from switching valve at start-up
Severity
Medium severity: the emission reduction system is disabled; no immediate driving hazard, but emissions exceed regulatory limits and the catalyst warms up more slowly.
What to do
- Read all DTCs and check for related secondary air system codes
- Inspect the switching valve A connector and wiring for corrosion, damage, or disconnection
- Measure solenoid winding resistance (typical: 20–40 Ω) with a multimeter
- Check supply voltage at the connector and the ECM control signal
- Replace the switching valve or repair defective wiring, clear the code, and verify operation