This replacement Combi valve fixes problems with your vehicle's secondary air system. In Volkswagens and Audi's, this is a common part to fail, and causes a check engine light to illuminate. This valve is controlled via engine vacuum and a solenoid to allow the secondary air pump to push air into the exhaust stream on cold starts. It reduces emissions and will cause your vehicle to fail an inspection. These valves get gummed up over time from exposure to the exhaust, or just fail internally.

Make sure to check the vacuum lines to it and the control solenoid, and replace those if needed. Also make sure to replace the gasket (ES#279362) when replacing the valve.