Replacing rear O2 Sensor

[Da Dark Jedi]

OK... I've just came from underneath the car tring to replace the rear O2 sensor. The originals are still in the car, so they've seen 14 yrs of Chicago weather. These bad boys need heat applied to remove, which I'm not comfortable doing. I'm curently soaking them down with penetrating oil. One sensor has a code and needs replacing, now here's my question. Would replacing the other side for good measure behoove me?

[OwnerCS]

I had one going weak so I replaced both on my 91. I picked up two different types of O2 sensor tools from Harbor Freight. As it turned out, the different tools performed better on each side.

[Q451990]

The rears are a check to make sure the catalytic converter is working. It isn't used for engine control - so I wouldn't say replacing them in pairs is absolutely necessary. Probably not a bad idea though.

Heath

[BadQ45t]

Mine just triggered the CEL and I replaced both of them figuring the other wasn't far behind. My car sits in a garage in California so no salt and not nearly the weather in Chicago but my mechanic popped them off and replaced the new ones in about 20 minutes flat. They popped right off.

[mcrews]

well, the don't 'pop' but they do unscrew pretty quick and easy. breaking them loss is a bit intemidating......but you really can't hurt anything

[Da Dark Jedi]

well, the don't 'pop' but they do unscrew pretty quick and easy. breaking them loss is a bit intemidating......but you really can't hurt anything

Thats putting it lightly. If I screw it up, the section that its in cost $790.00 to replace, the driver side $1066. I'll let the mech break them loose for me Monday. here is the part number for a 97 Q45.

Driver Side; 200116P100
Pass Side; 200106P100

So $50 bucks is for peace of mind. Also I need to re-new my state tags. Illinois emissions test won't touch the car with the CEL on, it's hooked up directly to the state. If yours have been in for as long as mine have see if they come out or turn.

[Q451990]

I'm pretty sure there's a threaded bushing between the sensor and the actual manifold. I know there is on the older Q, because I stripped it out and had to replace it. It basically looks like a nut with threads on the inside and outside. Outside threads screw into teh maifold, inside threads hold the O2 sensor.

Heath

[BadQ45t]

I didn't mean "pop" but I was yacking with him and they came off without any drama whatsoever.

[Da Dark Jedi]

Well heres the update on the repacement. Those things are rusted on so bad the mechanic could not get them off. The reason is, the section that its mounted in (both sides) had rusted so bad that when heat was applied the metal around the mount socket would melt. What I needed to do was go to a muffler shop and I have the section removed and a new one welded in its place, along with the mounting nut. Also what I noticed was, I was performing the removal process right, I never took inot account the rust. So after 1 1/2 I did notice the exhaust was a bit louder, this was due to a crack that had develope.

So after 14yrs of Chicago weather the under carriage looks pretty bad. In the future when I take on these jobs I will replace the whole unit that its attached to. I will also be performing a dose of penetrating oil Yearly. The other side will be done next week the O2 sensor is okay but that section (from what I was told is worst). Next step is front steering linkage.