Air Injection: Description and Operation

Secondary air system

WARNING: When doing any repair work, especially in the engine well, due to the cramped conditions, pay attention to the following:
^ Route all sorts of pipes (e.g. for fuel, hydraulics, activated charcoal filter system, coolant, refrigerant, brake fluid and vacuum pipes 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 valves for 100 seconds during a cold start (+5°C to +33°C Engine Coolant Temperature). This produces an oxygen-rich exhaust gas causes after burning and reduces the heat-up phase of the catalyst. Activation is initiated by the Motronic Engine Control Module -J220- via the secondary air pump relay -J229- to the secondary air inlet valve -N112- (Note 1) and combi-valve. The secondary air pump motor runs and opens the combi-valve at a pressure of 60 to 70 mbar (Note 2)

Also after each subsequent engine start (up to max. 96°C Engine Coolant Temperature)1 the secondary air system will switch on for 10 seconds during idle and is then monitored by the system. During this procedure the oxygen sensor must be active.
(Note 1) Only Engine Code AEG (through MY 1999 06.99)
(Note 2) For Engine Codes AEG (from MY 200O 06.99)1 AZG & AVH