I recently bought a 2019 plate A6 Avant. After 5 weeks the amber emission control system icon appeared and won't go away. It doesn't flash. I took it back to the approved used Audi dealer I bought the car from, who put it on a ramp for diagnostics.
They showed me a dent in the heat shields on the underbelly and told me that a communication was lost between X and Y (a sensor needed replacing). Their cost to repair is not insignificant.
They were able to pinpoint exactly what time and what day the fault light came on (through the diagnostics). This was exactly 5 weeks after I had bought the car.
My question (and please note that I'm no techy) is: could the problem have been there BEFORE the light came on, i.e. could the sensor have been damaged, and the fault light not shown up immediately. Could the damage have existed I bought the car. I don't remember any rocks being kicked up, nor scraping any speed bumps.
Thank you.