Code reader said o2 sensor heater circuit b1 and b2 downstream both not working. Wd it be sensors? Had rats gotten to my wiring ? Turns out fuse 11 Was missing. Did some wheeling a few weeks back on washboard roads and think it shook loose. Anyhow cdnt find for the life of me anywhere online that told me if or where the fuse for the o2sensor heater was. Well it’s #11 15 Amp. Under the hood. Hope this info helps some one out ! Next job the fuel sender units to replace !