Cats and O2 Sensors

So I just finished up a PS pump, Brake Booster and related hose install, looking at what's next.

I am original owner 2006 6L Denali w/175K. I have battled the typical P300 code but have never had a Cat or O2 sensor code. I do seem to have less power even after plugs/wires, TB clean but not due to any of that, just degrading over the years - I think.

From this forum, I've heard that clogged Cats can impact power/performance & that the rear 2 O2 sensors monitor the Health of the Cat's. Also, in RockAuto, Walker Cat Info states that "Catalytic Converters are designed to last the life of your vehicle – they do not fail on their own"

Is that true, the Cats don't fail unless impacted by other engine issue, heat, mixture, poor gas, oil sludge ?

If so, When should these O2 sensors be changed, I was waiting for a code - but I've changed on other vehicles way before 175K ?

Any thoughts are appreciated - Thanks.

technically yes a cat wont fail on its own. driving habits can also play a factor aswell. the regular carbon build up will generally get blown out by regular typical driving. if the driver of said vehicle is an overly cautious sunday driver type all the time it is possible for the exhaust velocity to not ever reach a point that will blow the carbon out. im not suggesting a vehicle should be beat on and raced but a typical grocery getter that never actually leaves town could be one such case. anyway numerous actual minor problems can cause premature cat failure much more commonly than what i above mentioned. i only mentioned it for the information not because its a big possibility. tune ups exhaust leaks blah blah have a bigger impact on proper exhaust condition.

Badwrench said:

"Catalytic Converters are designed to last the life of your vehicle – they do not fail on their own"
Is that true, the Cats don't fail unless impacted by other engine issue, heat, mixture, poor gas, oil sludge ?

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I would say thats not true. It's common belief that the lifespan is 100k miles or ten years. They do wear out.

Badwrench said:

If so, When should these O2 sensors be changed, I was waiting for a code - but I've changed on other vehicles way before 175K ?

Click to expand...

When they fail. I havent really found any information stating they can "wear out" with degraded performance, but not give a code. If it makes you feel better, you could change them sooner.

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Thanks for the replies, I never did get a P code for O2's but I just ran my Actron CP9180 O2 scan again & it doesn't say No Codes Found. It says No O2 information was retrieved from the vehicle, so maybe it can't check - rather than checked successful with no codes.

I'm gonna replace the 2 fronts with AC Delco because they regulate fuel/air performance and I suppose they could be impacted by carbon buildup.
@drakon543 - If the rears only measure Cat Health w/o affecting fuel/air ratio - Is it even important to replace them ?

if you have no codes i wouldn't be worried about replacing any o2 sensors. they generally dont like to come out nicely. ive had them break off in the exhaust or rip the threads out of the exhaust o2 bung. then your stuck fighting with it or buying an exhaust too.