After one week of lower temperatures (-24c max..)  I got this error "error adblue (def). no engine start in 1000 km". It disappears first two or three times but then stayed permanently there. Diagnostic returned error P20E800 and it was not possible to clear this code off. After looking under the hood I don't need guess what is wrong = there is leak on top of the adblue injector. Adblue feeding tube is cracked.. so booked repair for next week. Luckily car is under warranty. I'm surprised how weak this system is. That kind of cold is not uncommon here. It would be long winter if I need to go repair this adblue system after every cold night here

There have been a number of 'TPI's' issued across VAG related to the AdBlue SCR system.