Hi folks. Just picked up an 01 camry for my daughter and the previous owner told me the engine light was on due to an O2 sensor.
I just pulled the codes and got a p0401 twice and a p0420.
I did a search here and neither are related to the O2 sensor from what I've read.
Before I start replacing parts and chasing my tail I thought I would check here for suggestions.
If the cat is gone or going I can get it removed (no emission tests here).
The car works great, pulls good, idles smoothly.Previous owner was the original owner and he maintained it and he said his mechanic checked the code a few times and it was always the O2 sensor..and told him he didn't need to replace it.
Ya..I know. lol

 

Congrats for your new Camry...If you take good care of it it'll surely work better than before.

 

4 or 6 cylinder engine?

P0401 is an exhaust gas recirculation (EGR) problem. Not related to 02 sensor issues.

P0420 is failing cat performance.

There is a sensor before and after the cat to check exhaust gas condition going in and out of cat. If the cat is working the exhaust gas condition coming out will be different from that going in with this is picked up by the rear sensor. If there is no or little difference in condition the computer assumes the converter is failing. Or could be a bad sensor but they have their own specific codes.

If you take the cat off you will need to do something about the rear 02 sensor after the cat. Otherwise the computer will continue to assume the cat (now absent) is bad (condition of exhaust going into and out of cat is the same) and set a code.

There are devices that can replace the sensor to simulate a working cat, do an internet search.

 

It's a 4 cyl. I'm going to pick up a vacuum pump so I can pull vacuum on the egr and start the process of elimination. I pushed up on the diaphragm with the car running and it stumbled badly but didn't quit.

Thanks for the tip on the converter...never considered the downstream o2 sensor "looking" for it.