So I was reading th o2sensor post below. I'm interested in what exactly they are for. and since my cat converter needed replacing last week, I wonder what caused it to fail and where does the o2 sensor fit into that issue. I realize that could be a long story.Anyone want to spell it out for me? thanks
bc

 

What year, model and mileage on your truck? How mechanical minded are you?

 

I have a 98 disco w/115k. I'm a reluctant mechanic.That is I'de rather have a pro do most major work but I have been known to tear down an engine and rebuild it in my youger more adventuresome days. These days I can't afford dealer rates and don't have much faith in the mechanics I've used on my last disco.. besides that they charged 85bucks /hr. So I can actually do most work myself but haven't kept up to speed on engines since things got so computerized.
BC

 

The o2 sensors tell the computer how much fuel each bank of the engine is getting.
You have 4 sensors, two for each side. One before the cat and one after. It is basically a temp sensor, it senses how hot the exhaust gas is and that tells the ECU if left or right back is running to rich/lean/or correct for the amount of throttle/gear/road speed/engine RPM/engine load, etc.
If your O2 sensor fails and the engine runs to rich for to long it will overload your cat and cause premature death to the cat as well as excessive carbon build up in your engine.
Running leaded gas will kill a cat too.
That is the long and short of it, hope it helps. Oh yeah, cats can die from just old age too.