Greetings legends!

So have the dreaded P0430 (bank 2 catalyst sucks ass alarm), we all know that one. Came with a misfire. Changed plugs and coils all went away. P0430 did end up coming back eventually. So ran some diagnostics and found the the 2 downstream o2 sensors were way less voltage wise and stayed in a controlled small range at around 0.28. I'm thinking that appears normal and good sign the cats are working.

Now the upstream's behave differently. The bank 1 upstream is a huge range from 0.015 to 0.85 going up and down at all times frequently. The bank 2 upstream doesn't move like that. It basically hovers at 0.35 to 0.45 range. Testing was at idle. Hitting the gas they both move up and are close to 0.85.

As you can see here there is a big difference between upstream 01 and 02 graph wise....to the left is were i stepped on the gas.

I guess long story short, would it be reasonable to suspect the bank 2 upstream o2 sensor here as the first thing to check/replace? Or could there be other issues further upstream also worth checking?

***SIDE NOTE*** Mode 6 data also shows FAIL for Low and High sensor voltage for switch time calculation

Thanks as always for any fine person who has any knowledge/input suggestions!!!

Neither of your cats are warmed up enough for those readings to mean anything. The front and rear O2's will both be switching when the cats are lit. The ECM determines the health of the cat by comparing the front/rear switching rates when cruising. S2/S1 must be 0.75 or less, a higher ratio means the cat isn't doing its job. Your screenshot shows bias voltage on both rears, meaning they aren't warm enough and/or the RPM's aren't high enough for them to work. You need to take readings at a warmed-up cruise for them to mean anything.

VStar the legend in the house. I will say that wasn't off cold start, it had been running for 10 minutes and was up to regular operating temp. Just as added info, but i defer to your knowledge. What would be an ideal scenario to do live data on the o2's? Like literally driving for a half hour and doing live data as you go?

But with that said, would the fronts not just be measuring the air to fuel ratio and sending that back to the ECU? If something is off there would the cats need to be lit or a certain temp achieved first for it to matter when looking at upstream o2's? I do get what you're saying though that maybe what was done isn't enough for a good test on the downstream 02's to say the cats are good. I'll defer to your wisdom. And thanks for the reply as always.

I did get this one while running to eat enchiladas....

Thing is idling pretty rough at times now...Also threw a P0306 cylinder 6 misfire with the P0430. So all this stuff is bank 2 related. Put hand over muffler and pressure blew my hand off, no obvious sign of exhaust leaks. Also checked the fuel pressure regulator for the hell of if and no gas in the vacuum line.

Seems like a bank 2 cat blockage at this point, have an infrared thermometer coming tomorrow to see if it's hotter in the front. Any input or past experiences...feel free to hop in!

My main concern is replacing a CAT and figuring out later it only went bad due to something else.

The thermometer will tell you, just make sure it's fully lit before you test. Take it for a short ride, don't just idle it. If the outlet isn't significantly warmer than the inlet, the cat is dead and possibly blocked. You can also just pop the front O2 and see if it runs better. If it does, that cat has at least a partial blockage.

Infrared heat scan Both showed front higher...after driving and then holding 2k rpm's in the parking lot for 5 minutes. Smells like gas, and is struggling. O2 bank 2 S1 always looks suspect. I'm thinking it's feeding the computer a lean sitch at all times....I divert to master VSTAR if you have time to share thoughts. MAF maybe? Not sure seems lean conditions and gassy all the way....I suspected seeing the side with no codes hotter at the end, but both sides were hotter at the front.. I'm still thinking change bank 2 sensor 1 out as a first step and see what happens....could be drastically wrong of course.

If they're both hotter in front then they're both shot, especially if they're both hotter in front while the engine is misfiring. Unburned gas turns the a$$ end of a cat cherry red. I have to suspect one or both of yours are partially blocked.