Air Injection: Description and Operation

2665 Secondary Air Injection

Secondary air injection is activated by the Motronic control module. The air supplied by the secondary air injection opens the check valve when the pressure exceeds 80 mbar, the air is then blown through the lines to behind the exhaust valves of the respective cylinder heads.







The injection of secondary air leads to a reduction of the CO and HC pollutants that are increased by operating with Lambda < 1 while the engine is operated in cold start mode. Additionally, the catalytic converters achieve their activation temperature of approx. 662° F. (350° C.) more quickly due to the waste heat created during the after burning. Activation conditions are achieved during the first cold start process if the coolant temperature is between 14° F. (-10° C) and 107° F, (42° C.). When running close to idle speed, secondary air injection is active for approx. 60 seconds, for a partial load up to 80 seconds.

NOTE: Diagnosis: The secondary air system s function is monitored by the oxygen sensor control. The secondary air pump is monitored by the output stage diagnosis.

If during secondary air injection an intake air mass of approx. 732 lbs per hour (332 kg per hour) is exceeded, the secondary air injection is deactivated.

Secondary Air Pump Components