i recently had a code 131 and changed the top right side o2 sensor . this lasted about 2 hours (the no cel) that was just long enough to pass my emissions test ....thank god! anyhow, now i get a 420 code, is that the same side lower down? or am i way off? and why did it go out so quickly after the other one was replaced?

98 SE sport 2.5 dura atx-silver painted silver dash and red under the hood mesh grill, knauberized, aftermarket fogs, cone filter, alpine head unit 50x4