Celica Forums Thread Like Summary - Check Engine Light lingering problem

hey so i have a 2002 toyota celica GT. Every year when it gets cold, my CEL appears with a Po420 code. and once it gets warm outside is disappears. well i need to get my car inspected and i cant do so with this cel. did some research and saw that i could be an old catalytic converter or a faulty O2 sensor. Before i take it to get diagnosed at an auto shop, i wanted others opinion. since it is temperature related, wouldnt it be just a sensor? and if it is an O2 sensor how easy would it be to replace. Thanks

Would get rid of the P0420.

To add or replace the O2 sensor, jack the side of the car on passenger side up about 12 " and secure it on car stand. That would give you enough room to get under the car and access the O2 sensor on the pipe.

The pipe is extremely hot and sensor may be rusted or stuck. You may have to spray some liquid wrench on the threads and wait to loosen it. When putting it back, apply some antiseize high temp grease on the thread so it will be easy to tak eout next time.