Just looking for some advice. My 96 s10 2.2l has 242k and is a daily driver (about 90mi). For the last 2 winters I get an o2 code that's intermittent. Once the weather warms the eng light goes out. Since I am putting so many miles in, would it be smart to go ahead and replace both. They are factory originals. Thanks for any input
The O2 sensor only checks the levels in the gases going past it. Since the CEL is going out, then most likely they’re working, and there’s another cause for it coming on.
There are a lot of guys out here better at diagnosing fuel problems than I am. I can only have you search the board for O2 (or catalytic convert) related responses…problem is you’ll find hundreds if not thousands of hits.
I keep hearing throttle body, idle air control, all those other fuel related items, so you could check and clean those.
…if nothing else, maybe someone will correct me 
Good luck,
Chase
Get the O2 sensor signals measured with a graphing scan tool or a scope.
A good mechanic can tell if your sensors are good, bad or getting weak.
Or there’s another problem making the system work marginally.
A common misconception is that the error codes say a particular part is bad.
They only show where to do further investigation.
The actual code would be a tremendous help.
However, I’ve recently learned that sometimes when a cat converter is getting older and its efficiency drops, it can become insuficiently effective in cold weather. The catalyst’s effectivity is directly related to its temperature, and in cold weather a marginal cayalyst can not quite have sufficient impact to meet the “efficiency spec”, in short it won;t change the oxygen levels enough and the light trips. Some manufacturers, like Toyota, are now designing the primary converters into the exhaust manifolds, right where the exhaust exits the ports, to get better performance from the catalyst.
Without being able to connect to your data link, and especially without having the codes, I’m wildly guessing. But it’s a possibility.