Air Injection: Testing and Inspection

Secondary Air Injection System

The secondary air injection system improves the secondary oxidation within the catalytic converter which are 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 start-up 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, causes the after burning and reduces the heating-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 on board diagnostic functions.

For all secondary air injection system component locations, removal/installation procedures and torque specifications, refer to the service information.