Lost $180 on a bad O2 sensor replacement in Detroit last month

I swapped out my upstream O2 sensor on my 2012 Focus because of a p0420 code, and it turns out the part I got from AutoZone was dead on arrival. Spent 4 hours on my back in 30 degree weather swapping it in, only for the code to pop back on after 10 miles. Anyone else got burned by a bad part from a chain store?

3 comments

3 Comments

david_rivera419d ago

Check if your downstream sensor is the real problem. People get tunnel vision on p0420 codes and swap the upstream one first, but I had a similar issue on my old Mazda where the downstream sensor was actually reading funky and throwing everything off. Try swapping the downstream one too and see if the code clears, especially if you got a cheap universal part without the correct wiring harness. Did you check the heater circuit resistance on the new sensor before installing it?

the_xena16d agoMost Upvoted

OMG yes @elizabethg18 knows the pain, I did the SAME dumb thing on my Civic and wasted so much money!

elizabethg1819d ago

You know, I used to think the upstream sensor was always the culprit with P0420 codes, but you're right about tunnel vision. I was dead set on swapping the upstream one on my old Subaru and it cost me two sensors before I figured out the downstream one was reading way too rich and confusing the computer. Checking the heater circuit resistance is something I never even thought to do before I bought a cheap universal part years ago, learned that lesson the hard way when it was dead out of the box. Thanks for sharing this, it really changed how I look at these codes.