P0420 Catalyst System Efficiency Below Threshold, '00 Prizm

Recently (within the past two months) my Check Engine light has come on, had it checked at autozone and it was code P0420 Catalyst System Efficiency Below Threshold (Bank 1). I have a 2000 Chevy Prizm (nearly identical to Toyota Corolla). I'm wondering if the whole cat needs to be replaced, or just the oxygen sensor(s), how to check the sensors, what kind of cat I need (something like http://cgi.ebay.com/ebaymotors/MAGNAFLOW-CATALYTIC-CONVERTER-98-02-CHEVY-PRIZM-91004_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1205Q7c66Q3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318Q7c301Q3a1Q7c293Q3a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZitem330310053191QQitemZ330310053191QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories that?)

It has gone off a few times, only to reappear shortly (a day or two) later. Is this more indicative of the sensors, or the whole cat?

If it is not the sensors and is the cat, about how much am I expecting to pay to have this done? Is it something you can do yourself?

Appreciate all the help!

98% of the time, it's the cat.

Make sure you get a good quality cat as the cheaper ones don't last long...OE is preferred.

You didn't mention the mileage on the vehicle...check with the Dealership...most cats are warranted for 80,000 miles.

It's just around 75k miles. I bought it used from a friend who put the majority of those miles on, but he bought it used at <10k miles. How would I go about finding if there's a warranty still on it? Also, is OE a brand or is it some specific type?

Appreciate the help.

Call/visit a Chevy dealership and ask how long the cat warranty is.

Because it is an emission part, the warranty is good for the entire period, regardless of change of vehicle ownership.

OE means Original Equipment (dealership part). Many of the aftermarket cats (cheaper ones) skimp on the precious metals required for the cat to do its job...hence they don't last long and you're replacing it again.