Air Injection: Description and Operation

Secondary air system

WARNING:
When performing repair work, especially due to the confined conditions in the engine compartment, pay attention to the following:
^ Route all types of lines (e.g. for fuel, hydraulics, EVAP system, coolant, refrigerant, brake fluid and vacuum) as well as electrical wiring so that the original positions are restored.
^ Ensure sufficient clearance to all moving or hot components.

Function
^ The secondary air system blows air in behind the exhaust valve for a maximum of 100 seconds after the cold start (+5°C +33°C coolant temperature). This produces an oxygen rich exhaust gas which initiates after burning and reduces the heating-up phase of the catalytic converter.
^ Activation occurs from Motronic Engine Control Module (ECM) -J220- via the Secondary Air Injection (AIR) pump relay -J229- to Secondary Air Injection (AIR) solenoid valve -N112- [1], change-over valve and combination valve.
[1] Only vehicles with engine code AEG up to Model Year 1999, 05.99
^ If the secondary air pump motor is activated it produces an overpressure and opens the combination valve at 60 to 70 mbar [2].
^ 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 self-diagnosis. When doing this the oxygen sensor regulation must be active.
[2] Only vehicles with engine codes: AEG as of Model Year 1999, 06.99, AVH, AZG, BDC, BEV and BGD.