Air Injection: Description and Operation

Secondary Air Injection System

Function

The Secondary Air Injection system blows in air behind the exhaust valves during cold start (+5°C to +33°C Engine Coolant Temperature) for 100 seconds, maximum. This produces an oxygen-rich exhaust gas, causing after burning and reducing the duration of the catalyst heat-up phase. Activation is initiated by the Motronic Engine Control Module -J220- via the Secondary Air Injection pump relay -J229- to the Secondary Air Injection solenoid valve -N112-(1) and combivalve.

Also, after each subsequent engine start (up to a 96°C max. Engine Coolant Temperature), the Secondary Air Injection system will switch on for 10 secondsduring idle and is then monitored by the system. During this procedure the oxygen sensor must be active.

(1) Only engine code AEG