Get the app
Quick access from your home screen.
AV-SCANNER / Service function guides / Fuel and emissions
This guide covers the complete diagnostic procedure for a vehicle's secondary air injection system, from understanding its purpose and operation through testing the air pump, control valves, and passages. It is written for working mechanics and experienced DIYers who need a systematic, test-driven approach rather than parts-swapping. After completing the steps, the reader will be able to isolate whether a fault lies with the pump, the valve, the control circuit, or a blocked passage, and will know how to verify a repair before returning the vehicle to service.
Guidance is general and covers many makes. Exact procedures and values vary by model, so confirm them in the factory service information for your vehicle.
Download all 12 sections as a branded PDF to use in the workshop.
Get the app
Quick access from your home screen.