Secondary Air Injection System

The secondary air injection system improves the secondary oxidation within the catalytic converter due to the rich mixture during the cold start phase where the exhaust emissions contain an increased level of unburned hydrocarbons, thereby reducing harmful emissions. The heat released by secondary oxidation shortens the startup time of the catalytic converter considerably, as well as significantly improves emissions quality during the cold-running phase.

• During a cold start, the secondary air injection system injects air behind the exhaust valves. This produces an oxygen rich exhaust gas, resulting in a more complete burn of hydrocarbons while reducing the warm-up phase of the catalytic converter.
• In addition, the secondary air injection system is switched on (after a delay) during idle after every subsequent engine start (up to a maximum coolant temperature) and is checked through OBD functions.

For all secondary air injection system component locations, removal/installation procedures and tightening specifications, refer to the Service Information.