AGR Passat B6 140hp TDI

Hello,

My father-in-law has driven 21,000 km (approximately 13,000 miles) in his Passat, model year 2010, and now the engine check light has come on. The error code indicates a problem with the exhaust gas recirculation valve. VW has now ordered the AGR valve and, upon installation, noticed that all the pipes are heavily carbonized. They are now replacing the entire AGR system and installing a motor control unit update (VW's decision).
My question is: How can something like this happen in a car that's only 1.5 years old and has such low mileage? Could there be long-term damage to the engine? In theory, the carbon deposits could also form in the combustion chamber and potentially affect the valves and pistons. What do you think about that?

Hello, it's possible that the operating profile is mostly within the active range of the AGR (Abgastuchreinigung - exhaust gas recirculation) system: low load, low temperature, and a lot of water vapor?