420 code, ozygen sensor?front

code 420 is the catalyst efficiency code. You could be getting that code for various reasons.

 

This page has a little more info on the code.

http://allwheeldriveauto.com/subaru-check-engine-light-and-code-p0420-explained/

 

Can you provide any additional details on whether the car is running well or if there's any problems?

My 2000 forester popped the same codes, o2 and catty. i ran it a while like that then it started to buck (really sucks). id swap the o2 out it its poping o2 code.

car runs fine , 194,000 mi just code every 3 -4 weeks

The rear O2 sensor will be the one that would cause this code, so if you get tired of the code, you could try swapping the rear O2 sensor.