Hello! My oxygen sensor went bad because of some incident that happen awhile back. and now i am getting around to fixing it. and i believe a buddy of mine that works at a shop said its the O2 sensor. he also mentioned its the one in the front(somewhere under the hood). i went to autozone and had them run a CEL test and it came up as ........P0420: Catalyst system efficiency below threshold - bank 1. is that the O2 sensor, in the front? now he told me which one to get at autozone and it cost around 190? but i looked up o2 sensors online at other online stores and some came up as 30-40-50 dollars? am i looking at the right o2 sensor? because i am seeing two diff, or/and multiple price ranges for these? if anyone can help me out, id greatly appreciate it! and if anyone had the same problem, do you gals/fellas have any input where i can get this part for a good price. Thanks again!

 

O2 sensor is around $190 at Autozone for our car.......try hitting up junk yard for a wrecked tC first and you should be able to get one for about $30.
Do you have header.......that code seems like it is seeing cat failure......or lack there of if i remember.......

I know there is a listing of codes here somewhere that tells what they are.Give the search a whirl and see if you can find it.

 

That is an odd code to throw and say bank 1. I would think it would be the secondary O2 sensor failed, or the cat is damaged & the sensor reading the issue with the cat. P031 is generally the front sensor.

Most likley it is simply the secondary o2 sensor which is in the $40-50 range. The front generally runs around $190 as it is a 4 wire heated sensor.