AdBlue is injected into the exhaust system, where it transforms into ammonia and interacts with the combustion-generated nitrogen oxide gas to transform it into the non-toxic gases of nitrogen and oxygen. Back home, took it in to my mechanic and said the NOx sensor was bad and wants $8-900 to replace. How many of us will curse, Come on, officer! (despite being dry for weeks). ad[14]='https://www.vwaudiforum.co.uk/forum/images/Banner/rac.gif' It is advised to use the AdBlue pump designed for passenger automobiles when filling up at a gas station.