I replaced both sensor 2s on both banks of my GF's Denali when she got check engine light at 101K. The codes read O2 sensor, bank1 sensor 2, and bank 2 sensor 2. I replaced them with direct fit Bosch sensors and cleared the codes. The CEL came back on and has stayed on. It is saying heater circuit for one of the sensors, maybe both. I don't have the truck in my shop right now. what do I have to do to fix this heater circuit issue? She wants me to just replace the sensors, but she doesn't understand that this issues is not likely the sensors. They are under warranty and I will replace them when I know how to fix the whole problem. any ideas? Sorry for the patchy info, when I get it on the scan tool again, I post the exact codes.
BTW it's a 2002 Yukon XL denali with AWD and a 6.0.