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Discussion Starter · #1 ·
(As mentioned in my EGR problems post, I had an MIL on and off for a year now indicating a rear O2 sensor problem)

Well I finally got around to removing the rear O2 sensor from the Cat... here are some tips for anyone who is thinking about doing this... This is mostly for newbies like me...

1. All the parts in the exhaust system tend to get rusty rather quickly... use penetrating oil liberally and if something doesn't turn with a reasonable amount of force, then don't overdo it! I've put two holes in my exhaust system doing this... one removing the shitty shielding and one in the cat now (I twisted too hard and now the threads are completely torn apart in the Cat). If you can't turn the bolt, use more oil and wait. If that doesn't work, spare the money to have it done professionally... because they have better experience and tools (plus if they screw up and tear a hole in your pipes, they're liable and will have to replace or repair it for no charge!)

2. Don't use front-mount ramps to do this... you won't have enough space under the car to get proper leverage and you will probably not be unscrewing straight.

3. If there are a lot of contaminants (basically rusted crap or oil) that come out with the O2 sensor, you probably have a crapped out Cat AND you will have to replace the sensor. Remember that oil in the cat might denote a leak somewhere, same with white residue (from coolant).

4. Try running your car with the rear O2 sensor out... then check the hole from whence came the sensor. If the residue is gone and it seems dry, you might be able to get away with simply replacing the sensor.

5. The sensor MIGHT be salvageable. I cleaned mine with soapy water then shook the hell out of it, blew through it and left it out to dry. It seems to be working, but since the problem was intermittant, it might not show a problem for a while.

I'm by no means an expert so if anyone has any comments feel free to add your wisdom...

I think this at least is better than the idea of letting the MIL burn out though...


freakish poster
1,236 Posts
You can best remove an 02 sensor easily when it's burning hot. Of course it may be unsafe depending upon where it's located.
edit, unsafe as far as burning yourself.
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