| Because of the over-enrichment of the mixture in the cold start phase, the proportion of unburned hydrocarbons in the exhaust gas is higher. The secondary air system improves the afterburning (oxidation) process in the catalytic converter, and thus reduces toxic emissions. The heat generated by oxidisation accelerates the “light off” of the catalytic converter and significantly improves exhaust gas quality during warm-up. |
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| During the cold start phase (coolant temperature at +15 ... +35 °C) the secondary air system blows air behind the exhaust valves for approx. 65 seconds. This produces an oxygen-rich exhaust gas, causes afterburning and reduces the heating-up phase of the catalytic converter. |
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| In addition, 20 seconds after each following engine start (until coolant temperature reaches 85 °C), the secondary air system switches on for 5 seconds when at idling speed and is checked by the self-diagnosis. |
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| The secondary air pump motor -V101- is actuated via the Motronic control unit -J220- and the secondary air pump relay -J299-. |
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