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.
Secondary air injection (AIR) system: Function
During cold start (+15 ° C to +35 ° C coolant temperature), air is blown behind exhaust valve by Secondary Air Injection (AIR) system for 65 seconds. This produces an oxygen rich exhaust gas, causes afterburning and reduces the heating-up phase of the catalytic converter. Activation is triggered by the Motronic Engine Control Module (ECM) J220 via Secondary Air Injection (AIR) Pump Relay J299 to Secondary Air Injection (AIR) Solenoid Valve N112 and combination valve. 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. 85 ° C engine temperature) and is checked via On Board Diagnostic (OBD).
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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.