Where is the secondary air valve of Audi A6 located?

[RonanFitz]

Audi A6's secondary air pump is located behind the front bumper on the passenger side. Basic function of the secondary air valve: The secondary air valve works by introducing fresh air into the engine's exhaust gases, increasing the oxygen content in the exhaust. This allows unburned HC (hydrocarbons) and CO (carbon monoxide) in the high-temperature exhaust to undergo secondary combustion and oxidation, thereby reducing exhaust pollutants. It is a type of engine post-treatment technology. Working principle of the secondary air valve: Under different operating conditions of the vehicle, the amount of supplemental air required for combustion and oxidation in the exhaust varies. Too much supplemental air can cause issues like backfiring in the exhaust pipe, while too little will fail to achieve the desired oxidation and combustion of pollutants. To ensure the appropriate amount of supplemental air under different conditions, a "control valve" is installed on the secondary air valve. The secondary air valve utilizes the negative pressure created by the high-speed flow of exhaust gases from the engine to draw fresh air into the exhaust.