On-Board Diagnosis System II - Volkswagen Technical Site
On-Board Diagnosis System II - Volkswagen Technical Site
On-Board Diagnosis System II - Volkswagen Technical Site
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<strong>System</strong> Components (Gasoline Engine)<br />
The secondary air system<br />
3<br />
2<br />
1<br />
4<br />
5<br />
6<br />
7<br />
175_067<br />
Legend:<br />
1 Motronic control unit<br />
2 Secondary air pump relay<br />
3 Secondary air inlet valve<br />
4 Combination valve<br />
5 Secondary air pump motor<br />
6 Primary catalytic converter probe<br />
7 Catalytic converter<br />
Due to over-enrichment of the mixture in the cold<br />
starting phase, an increased level of unburned<br />
hydrocarbons occurs in the exhaust gas.<br />
Secondary air injection improves postoxidation in<br />
the catalytic converter and reduces pollutant<br />
emission.<br />
The heat released as a result of postoxidation<br />
shortens the response time of the catalytic converter<br />
considerably, with the result that emission<br />
quality improves greatly.<br />
32
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