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.
Your mechanic's speak in fluff, no specifics. Might be because you are not yet learned about cars.
Go on Amazon and get an OBDII adapter that will work with your phone and download Torque Pro or something similar.
Now YOU can pull up the codes yourself and not rely on someone else.
The only time a cat converter code is a false positive is with a massive exhaust leak in front of it. A cat code does not mean it's time for new sensors. Having said that, at 189K miles, yours are 89K miles overdue for replacement. $180 or so delivered for all 4 plus labor or tools if you DIY.
Cheap Chinese Communist catalytic converters do not last. I replaced mine with a Magnaflow Y-Pipe and Cats almost six years ago and still going strong.