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Replacing downstream o2 sensor

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15K views 13 replies 5 participants last post by  16SixSpdElantraGT  
#1 ·
Anybody replaced the downstream o2 in their egt? The 4 wires appear to run up into the chassis. Just trying to figure out if I need to remove the black plastic cover under the car on that side to access them or if it's more involved than that. My new sensor should be here by end of week so I'm just trying to get a game plan together.
 
#2 ·
2001 Elantra owner here
Don't know about your car
But my car, the O2 sensor was a bear to get out
I tried the O2 sensor wrench ... failed
I tried it with cheater bar ... failed (broke the O2 wrench)
I tried to remove it with a plumber's pipe wrench ... failed
I tried using propane to heat it up and pipe wrench ... failed
Finally I took it in to a garage and paid fifty dollars to remove the darn thing
Oxy-acetylene torch and pipe wrench, they got it out (20 minutes)
The O2 sensor looked like it had no threads
This is wear and tear of living in the salt belt.
Got a thread chaser to fix the threads on the pipe and put in the new O2 sensor
I never want to do that again

Good luck to you
 
#5 ·
The factory don't use enough, if any, thread dope on these. It can be a southern car and have the same issues with being stubborn. We just heat them cherry red and spray with a little water and they come right out. On real bad ones you may have to repair or replace the bungy.
 
#3 ·
When i replaced mine on my Accent this summer the threads stayed in the pipe. You will need a tapping, not chasing, M18x1.25 thread cutter. Most are just thread chasers and will not start. I had to use a 3/8" NPT pipe tap to get some threads started for the thread chaser.


Fixed my P0420 though. That and a O2 extender.
 
#6 ·
I had to relocate the upstream sensor to accommodate a custom header and it was a pain to get out so I think I'm ready for that part.

Its throwing code for bank 1 sensor 2. I forget the code number though. 58000 miles. I would just take it to the dealership but they will find a reason to not cover it and charge me. Not a fan of the dealerships around here and since I just finished my catback exhaust a couple weeks ago they have plenty of things to blame the failure.
 
#10 ·
BTW if the code is for the cat the sensor is probably not going to help. The post cat sensor should have very little activity during normal operation. It will usually read low (lean) as the cat stores O2 when converting well. When it degrades it doesn't store O2 and the sensor will start reading like the front sensor and that will flag the dreaded PO420 cat efficiency code.
 
#14 ·
The connector for the downstream o2 is located on the passenger side under the middle console closest to the firewall. There is a small panel that comes off and it's right there. I was worried it might be more buried than it actually was. Overall it only took about half an hour to replace.
 

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