What P0415 means
Secondary Air Injection System Switching Valve B Circuit Malfunction
How to diagnose
- Read freeze frame data. When P0415 set, your ECU snapshotted every sensor at that moment. This tells you what the car was doing when the fault triggered — RPM, load, coolant temp, throttle position, fuel trims. Almost always enough info to figure out the cause without further testing.
- Check for related codes. If you have P0415 plus other codes, fix the earliest one in the chain first — a single root cause often triggers multiple codes.
- Cheap fixes first. For most codes, the order is: inspect connectors + wiring (free), check for vacuum leaks (cheap), replace sensor (moderate), replace mechanical part (expensive). Follow that ladder before dropping money on parts.
Manufacturer-specific descriptions
Different manufacturers use P0415 for slightly different failure modes:
| BMW | Secondary Air Injection System Switching Valve "B" Circuit |
| FORD | SAI System Switching Valve B Circuit Malfunction |
| MITSUBISHI | Secondary Air Injection System Switching Valve B Circuit Malfunction |
| NISSAN | Secondary Air Injection System Switching Valve B Circuit Malfunction |
| VOLKSWAGEN | Secondary Air Injection System Switching Valve B Circuit Malfunction |
Read P0415 on your own car
DIY Fix My Car reads P0415 plus 25,000+ other DTC codes with manufacturer-specific descriptions. Includes freeze frame data, likely fix parts, and AI mechanic chat. Download free.