Air Injection: Description and Operation

Secondary air system

WARNING: When doing any repair work, especially in the engine compartment, due to the cramped conditions, pay attention to the following:
^ Route all sorts of lines (e.g. for fuel, hydraulics, evaporative emissions system, coolant, refrigerant, brake fluid and vacuum lines and hoses) and electrical wiring so that the original positions are restored.
^ Make sure sufficient clearance to all moving or hot components.

Function
The secondary air system blows air in behind the exhaust valve for 100 seconds during a cold start (+5°C to +33°C coolant temperature). This produces an oxygen rich exhaust gas, causes after burning and reduces the heating-up phase of the catalyst. Activation occurs from the Motronic control module (J220) via the secondary air pump relay (J299) to secondary air inlet valve (N112, change-over valve) and combi valve.

Additionally, after each subsequent engine start (up to max. 96°C engine temperature), the secondary air system will switch in for 10 seconds during idling and will be checked by the On Board Diagnostic (OBD). When this occurs, the oxygen sensor control must be active.