Cat, O2 Sensor, or nothing?

[Donf]

Yet another PO442.
This is the Tahoe that had the bad spider last year, it was replaced along with the cap, rotor, plugs, wires, fuel filter, PCV valve/hose and Idle Air control valve.
Once all was changed and the car ran fantastic, (the only thing I question is that it takes about 1/2 second to 'catch' when I crank it, I remember it starting instantly when new. Thinking a new distributer someday).
Until early January when the CEL came on.

When I checked it with my code reader I got a 0442. B1S2
Now it was dripping fuel out the exhaust pipe for a year or two prior to the above mentioned repairs being performed and I always figured that a cat was in the near future but it ran so strong, even at high RPMs, that I figured I may have dodged a bullet. It has continued to run well so that when I saw the code I thought that it might be my downstream O2 sensor on the previously afflicted bank as that seems common. I did investigate with my rudimentary code reader (screen shots attached) but they look fine to me. Also, after about 6 or 8 weeks, the CEL is gone and the reader shows all is well.

If I remove them I'm not going to attempt any diagnostic tests with them, their low cost makes that seem like a waste of my time. I'm thinking that if I replace one 22 year old sensor I might as well change all four. And I'm tempted to do so but I figure that original sensors aren't going to come out without a fight. Likewise the cats. However, I'm a charter member of the "If It Ain't Broke, Don't Fix It" club as any unnecessary work always causes trouble.

Still, I'm wondering what could have caused the code to pop up and then go. Any ideas?

Thanks, Don

 

[YukonGTmaster]

I had my check engine light go on when I drove on a highway that went from 3000ft down to Sea level. Calgary AB to Vancouver BC Canada. Then it would go out after driving around for a while. I did this trip a few times, and it always latched a light when I went from high elevation down to low level. This was before I had a OBDII scanner. The light came on again, I ponied up and bought a scanner. It was a bank 2, O2 sensor. I replaced just the one bad sensor (It looked how you would imagine it would after 20+years) and that fixed it for good. Knock on wood.

 

[mb1500]

The issue you describe is a cat code below threshold. The code you mentioned seems to reference EVAP.

The threshold is constantly running analysis and if the code cleared itself than no worries.

Cat efficiency code does not necessarily = clogged (restrictive) converter, simply the perceived air cleaning effect (2nd sensor reading compared to 1st).

They are self cleaning, sometimes a good long drive will build up enough sustained heat to clean off whatever contaminants and restore your efficiency.

Don’t use any snake oil. If the engine runs well, no codes, than no need to replace any parts.

 

[BG1988]

I had my check engine light go on when I drove on a highway that went from 3000ft down to Sea level. Calgary AB to Vancouver BC Canada. Then it would go out after driving around for a while. I did this trip a few times, and it always latched a light when I went from high elevation down to low level. This was before I had a OBDII scanner. The light came on again, I ponied up and bought a scanner. It was a bank 2, O2 sensor. I replaced just the one bad sensor (It looked how you would imagine it would after 20+years) and that fixed it for good. Knock on wood.

if it has a Baro sensor (if equipped)make sure it matches to the MAP sensor (key on) this can also produce a CEL when changing altitude.. if one of those sensors are broken