My son has a 2007 a3 2.0 170bhp tdi sline bmn engine the fault code that came up today when he put the code reader on the car, was p0546 been looking on net it seems to do with Exhaust Gas Temperature Sensor saying that it could be this sensor which i take to be the lambda sensor, been looking on the net and it seems that there could be 3 sensors that could bring this code up would anybody have a clue on what would have made this code come up and if so how many sensor are on this car and where they are also what my son should be looking at to replace thanks for all your help.