Change 02 when changing Cat ?
 

Is it usually necessary to change the 02 sensor when you are having the Catalytic Converter replaced?

No, you don't need to change the o2; unless the o2 is malfunction.

how many miles do you have that your changing your cat?

160,000 miles and counting

I got the P0420 code with the CEL coming on intermittently, and now it stays on

nice. I just hit 101k and was wondering how long they would last. The car feels a little sluggish sometimes an i wonder if it is related to that. I already changed the plugs, cleaned the intake manifold and ran seafoam through everything 2k miles ago. Car has never thrown any codes yet.

Cat problems can definitely make a car sluggish
My buddy had a mechanical tell him the cat was the problem with an impala that had 125K and no check engine light?????? it fixed it

My check engine light would come on and the car would immediately feel sluggish and/or constipated, it would go off and ride better.

I got tired of it and changed the cat, hopefully the CEL goes off soon.....

My cat lasted approximately 100,000 miles, just barely missed the 80k mile federal warranty. As for my O2 sensors, I am still on my original ones at 170,000 miles without any signs of trouble. Don't understand how some manufacturers recommend changing them things so often, it seems like they last a lifetime on these cars.

Resetting P0420 code afetr replacing cat?
 

I just replaced my cat with a Random Technology high flow cat (183-20002). My 99 TL started giving me a P0420 code at 88K miles but I just replaced the cat at 155K. Should I reset the P0420 code with my scanner or let it clear itself?

I got my CEL with P0420 code. How can I reset the OBD code without a scanner?

Pull the Clock backup fuse on the passenger side dash fuse panel for 10 min.

I was told that a scanner shows when a system was reset - that's why I needed to drive 40 miles after a reset before taking her back to the emissions inspection. Does this 10 min fuse trick show a reset on the scanner?

Yes, that is only to erase codes and the CEL. Testing equip will show that the ecu was reset and if it doesnt meet the requirements they will fail you and tell you to come back.

:werd:
196K = OEM CAT, OEM 02 Sensors... Pass Emission Tests with flying colors...

I just wrote about the special driving procedure in another thread- for after ecu reset and headed for smog test
Need to run the engine thru every condition,,not just cruise around 40 minutes and think its recorded enough data for inspection

most of us are going with `1 minute` of clock fuse removal will clear and reset the ecu
You can disconnect the battery neg cable instead but that requires radio code input,,
while clock fuse is the secret backup power to ecu and doesnt affect radio `security`
(disconnect batt and radio thinks its being stolen)