| The over-enrichment of the mixture in the cold start phase produces a higher proportion of unburnt hydrocarbons in the exhaust gas. The injection of secondary air improves the post-oxidation in the catalytic converter and thus reduces pollutant emissions. The heat produced by the post-oxidation considerably shortens the start-up time of the catalytic converter and significantly enhances the emission quality in the cold-running phase. |
| The engine control unit activates the secondary air pump motor -V101- via the secondary air pump relay -J299-. The stream of air from the secondary air pump opens the combination valve for secondary air and permits air to flow into the exhaust system upstream of the catalytic converter. |
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