How urgent is to change broken catalyst converter and oxygen pump?

I have 2002 Mitsubishi Galant (ES) 136K miles. There was 'Service Engine Soon' light on for around two months. It use to go and come back again but last two months it was continuously on. I showed my car to mechanic and he told me that your catalyst converter and oxygen pump is broken.

My question is how urgent is to change this?How urgent is to change broken catalyst converter and oxygen pump?
If it's still running ok.... I'd say get it done when you can... but eventually it's going to start throwing your ECU off, loose some fuel efficiency, and foul your plugs quicker.



- Good Luck!How urgent is to change broken catalyst converter and oxygen pump?
I believe you mean catalytic converter and oxygen sensor.



Both have a major influence on engine performance.



A clogged or malfunctioning catalytic converter will eventually prevent you from being able to start the car and have it run. The oxygen sensor will also affect your engine performance.



If you're going to keep the car, I would suggest having both replaced. It will be costly as a catalytic converter is quite expensive and when replaced, sometimes the surrounding exhaust components will also need to be replaced.
just use it till its stops[if it ever does]..it will be needed sorted for its next mot though...oxy pump[not oxy sensor as another answer mentioned] is simple enough to change,the cat may cost a fair bit..when its time i advise buying a second hand cat from a salvage yard..it will cost a 10th of a new one.