Reverend Red Bull
That code is related to the DEF reservoir heater. It's usually accompanied previously by P21dd when the heater itself is bad. Since P20B9 is an open circuit code, you could have had an immediate failure of the heater or the module which controls it or the related wiring. Looks like you're still under B2B warranty, so you should have no problem with coverage or the loaner car, if your warranty details are the same as the U.S. Even outside of the B2B warranty, this would be covered under the 10 year/120,000 mile special coverage, this would continue to be covered, as long as it turned out to be a problem with the reservoir or one of its integrated components.