So i'm getting this cel u059f. I scanned it and it said Nox Sensor b is bad. Can anyone give me a link to buy one. I called my local dealership and the tech doesnt know if B is the top or bottom sensor. I'm guessing bottom since its b not a. He quoted me $500 for the bottom. IF i have to pay 500 for a sensor im deleting the truck right now. I'm at 99k miles anyway. Can anyone help?