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replace o2 sensors?
Posted: Wed Jul 29, 2020 12:12 pm
by jeff_j1701
Hello,
Is it difficult to replace the 02 sensors in a Vibe?
I recently had the exhaust manifold and catalytic converter replaced in my '07 Vibe (FWD) and I am still getting a P0420 code.
The mechanic said not to bother changing it on an old car (he has an '05 Vibe) as the car is still very driveable.
Would it harm the car if I don't change the 02 sensor?
If I do change it, is this something that can easily be done by someone who isn't mechanically inclined?
Thanks!!
Re: replace o2 sensors?
Posted: Wed Jul 29, 2020 1:46 pm
by joatmon
Did the shop clear the code when they replaced the cat? If not, and it was done recently, it takes several driving cycles for the code to clear itself
Re: replace o2 sensors?
Posted: Wed Jul 29, 2020 5:08 pm
by jeff_j1701
It was replaced almost 2 months ago, and it was cleared by him and me.
When it came back on, I just left it until I had the new manifold put it; cleared it 3 times since.
Re: replace o2 sensors?
Posted: Wed Jul 29, 2020 6:00 pm
by joatmon
too bad, I was hoping for an easy fix.
First off:
NEVER ever work under the car when it is jacked up unless you are positive it can't fall on you
I've replaced the one after the cat, I disconnected the connector inside the car (on the left side of the front passenger footwell)

- O2connector.jpg (90.06 KiB) Viewed 2593 times
then pulled the rubber grommet and wire through the floor, and threaded a box end wrench over the wire to get to the sensor. Looking at an old thread I used a 7/8" box wrench, that's pretty close to 22mm.
If I remember right, it took some force to get it started

- O2pipe.jpg (73.99 KiB) Viewed 2593 times
I've never tried the one on the exhaust manifold, I expect the main difference would be physical access to the thing
Re: replace o2 sensors?
Posted: Thu Jul 30, 2020 2:58 am
by zbyers
Since the manifold and cat were both replaced recently, removing the o2 sensors from the pipe exhaust shouldn't be too difficult.
However, RARELY, does P0420 mean it is an o2 sensor. Nearly every time it is the cat, as that code is saying the o2 is working, and it's detecting the cat is below efficiency parameters. Like I said, it's possible, but not very common at all.
What cat did you install? Have you pulled the live data to see if the o2 sensor is wonky? Have you tried simply removing the sensors and cleaning them up to see if that'll fix it?
Re: replace o2 sensors?
Posted: Thu Jul 30, 2020 4:45 am
by jeff_j1701
TBH, I forget what catalytic was put it. All I remember was it was a Walker. How do you pull live data from it, and what would that show?
I didn't know you could clean o2 sensors.
Re: replace o2 sensors?
Posted: Thu Jul 30, 2020 7:42 am
by zbyers
Well, if you have a code reader that can read live data, you put on the o2 sensors, and it will show you the graphs to determine how the sensors are working. This is something most garages can do.
Yeah, you could try cleaning them. Pull them out and hose them off with some brake part cleaner. There's no empirical proof that cleaning them solves issues, but it never hurts to try.
https://www.youtube.com/watch?v=afio03Sv_MU
Re: replace o2 sensors?
Posted: Thu Jul 30, 2020 10:52 am
by jeff_j1701
From the sounds of it, it's probably the downstream sensor that may be the issue.
I found Denso 234-4209 on Amazon for $57 (without connectors) would it be ok to use my current connectors or get a sensor with the connector? I don't know enough about cars to know the difference.
I might as well replace the sensor, as my car has over 320,000 (about 199,000 miles) km on it.
it doesn't look too difficult to replace the sensor, but do I have to hoist the car? I don't have any jack stands either.