[FC]

I did use liquid wrench but only gave it a couple of hours to penetrate. The can says to wait a few minutes. I guess I should have done it overnight.

Removing the secion of exhaust would have been an annoying and long job. If the new ratchet+liquid wrench did not cut it, I would have moved on to torching the pipe and freezing the socket (something that has worked for me before). I just did not have the jeep high enough off the ground to safely use the torch. The last step would have been what you suggest. I was starting to get concerned that it would require more torque to get the sensor out than the exhaust could bare in situ. The sensor was located in the middle of a pretty long span between supports.