I have had this code before on a CA emissions sentra and it can become a pain. To pass emissions testing, no cel should be illuminated or automatic fail. They also test your evap system by drive cycles, we do that at our work.
To trick the o2 after cat sensor, you need to have it detect CO and O2 based upon voltage readings. If you were to trick the PCM, you would need to get a spak plug anti fouler, then possibly rethread it to fit the o2 and give it just enough to read correct 02 flow. Your code is telling the PCM that your cat converter is basically "toast". Another method I have heard from on here is to get a pcm tune performed to ignore the rear o2. I strongly suggest you just replace the cat and rear o2 together. The 2 alternatives I mentioned to trick it is nothing more than a "band aid" to a deep cut wound. They may come back or cause future issues. From a tech perspective, replace the cat and rear o2 sensor and have the pcm reset of codes.
2009 Cobalt LS XFE U74
Mods: K&N Typhoon Intake, Option Cat-Back Exhaust, Cosmo Short shifter, Maxxim Ahead 17X7's, MPx shorty antenna, FE5 Strut/shocks, Tein S Techs, Moog endlinks, Moog spring seaters, ZZP shorty header, LSJ downpipe, LNF front grille