O2 Sensor Bank 2 Sensor 1, and Fuel Air Metering?
#16
#18
Bank 2 sensor 1 should be driver side before cat. Bank 2 sensor 2 is after cat. Bank 1 sensor 1 is before cat on passenger side and bank 1 sensor 2 is after cat on passenger side. If going from the top and it's tough to get off with a wrench, buy a crowd foot, use your ratchet wrench with a cheater bar. More to than 12in wrench will give you. You don't need dealership to fix lean or rich mode as the ecm controls that. You have a bad sensor which is causing your truck to rich or lean out, it's not the factory tune giving you the cel.
#19
#20