Downstream sensors solely used to measure pre-cat efficiency. Front bank sensors can be seen on exhaust behind rad (downstream points towards driver's side), rear bank downstream sensor is visible by looking under car in front of exhaust flex pipe.
Posting actual CEL code may help get you advice, alternately search using PXXXX format for actual code to see past threads.
p.s. Edit button active for one hour after post for error corrections or additions.
