Hello, I have a 2009 Tahoe 2wd 189,000 5.3 and I brought it to my mechanic because it has had a cel light on. The light has been on for a couple of weeks but no problems with the Tahoe runs smooth, smooth idle everything. He says Cyl 4 says a misfire so he ran it for a little no misfire nothing wrong. Also, he says there are 4 codes about the O2 sensors he says. He doesn't do exhaust but I asked the shop up the street he says it sounds like the cats are going bad. The shop up the road is a fee to diagnose so I haven't brought it up there yet. Does this sound like the cats or a sensor problem? Just tryna see where to start.