P0420 code from check engine light 2000 Mazda Protege?

It can be expensive depending on the car. On yours, probably only a couple hundred. If your protege is anything like most Mazdas, the entire exhaust system is flanged, which makes replacing it yourself easy, as sections bolt up to each other, rather than being welded or clamped. As you don't say what the code actually says, or any symptoms the car is having, further diagnosis here is impossible.

Yes cats can become saturated and stop converting gasses. They can also break and block exhaust flow. Those are really the only to failure modes for a cat. Either way means it needs to be replaced.

--Jas> Got this code and it says something abt catalytic

Well here is what P0420 code means when Googled

OK..... is it possible it may be something cheaper such as O2 sensor? And should I go ahead and change that out first anyway?

I'm unemployed and money is tight right now...hence the dumb questions

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

At 140k you are at the threshold of the cat. They do burn out. You need the computer scanned for other codes. The 02 sensors are monitored closely be the computer and the state of them determined. Absent of other codes you very likely have a bad catalytic converter.

For the air we breathe it is important to get this fixed but as far as car function the only difference you should notice is the red light glowing at you. Were it mine I wouldn't worry about it until I was back on my feet again or until I was coming up on an emissions inspection.

Steve B.

OK thanks

What does that mean exactly?

it means the the computer ramps up idle in cold start when the ambiant temp is at the predetermined value and does so that the cat, gets warmed up faster

reduc> philthy wrote: