Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Principle And Function
Principle
Due to the rich mixture during the cold start phase, the exhaust emissions contain an increased level of unburned hydrocarbons. The Secondary Air Injection (AIR) system improves the secondary oxidation within the catalytic converter, thereby reducing harmful emissions. The heat released by secondary oxidation shortens the startup time of the catalytic converter considerably, as well as significantly improves emissions quality during the cold-running phase.
Function
- During cold start (with coolant temperatures +15 to +35° C), the Secondary Air Injection (AIR) system blows air behind the exhaust valve for approx. 65 seconds. This produces an oxygen rich exhaust gas, causes the after burning and reduces the heating-up phase of the catalytic converter.
- In addition, the Secondary Air Injection (AIR) system is switched on with a delay of approx. 20 seconds during idle for 5 seconds after every subsequent engine start up to max. 80° C coolant temperature and is checked via On Board Diagnostic (OBD).
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.