How to replace upstream O2 sensor

[tlknv]

I need to replace upstream O2 sensor on my Subaru Forester L 1999. Do I need to remove the shield under the catalitic converter or it's possible to unscrew the sersor with some kind of "socket" wrench ? All the bolts which hold the shield are very rusty and I'm not sure if it's possible to unscrew them.

[danielsatur]

The upstream H02 sensor is the sensor closer to the exhaust manifold, it's the size of a spark plug, and canbe taken out with a wrench.

[tlknv]

Danielsatur,
Thank you for the answer. I just want to make sure that it should be some special/socket wrench. Shouldn't it ? It's impossible to unscrew upstream O2 sensor with any regular wrench.

[danielsatur]

Disconnect H02 sensor, thread a good boxed end wrench, and turn counter clockwise to remove.

Don't forget to put anti sezie compound on the threads of new sensor.

[tlknv]

Thank you, Danielsatur.

[tlknv]

Danielsatur,
Thanks for the info.

[tlknv]

Dear moderator,
It's my third attempt to just say thanks to the author of the answers.

[whopperdad]

if too rusty try using aero-kroil or pb blaster let sit a little while