Gomer1

Hello all, I have an '01 RX with ~113K miles. For a couple of months now, when I have the steering wheel all the way to the left, on a stopped car, and I give it gas, the VSC will kick in. Today, driving normally, VSC and CEL came on. I checked it to see what codes it was throwing, and to my amusement, the computer blame it on a bad catalytic converter. I got the lights reset and they haven't come back. What gives? -TIA

Lexmex

What was the specific code you received?

Gomer1

Well, the light came back again, after ~200 - 300 miles. This time I was able to note the code. It is P0420 Bank1 and says something about a bad cat. Is this an O2 sensor? I really hope it's not the cat.

-TIA

Lexmex

It can be related to a bad cat, but O2 sensor is also in play here. I'd tell you that the easiest way to take a look is if you have someone with an advanced OBD2 scanner or someone who has a laptop program that can read the readings on Bank 1, Sensor 2, the one after the catalytic converter below the vehicle.

That 420 code was common in Mexico and really had more to do with the gas quality and bad air making poor combustion. Sometimes it comes and sometimes it goes.

Gomer1

Yikes, this is no good news. I don't have anyone with that advanced scanner to check it :-( I found a similar problem in the ES300 forum, and the solution does not seem clear:
https://www.clublexus.com/forums/es3...-bank-1-a.html

Lexmex

Most competent mechanics in the U.S. will have such a scanner and you can see if they can get any numbers or readings on the scanner.

Generally, if after clearing the code, disconnecting the battery several times and still this code comes up WITH a functioning O2 sensor (meaning that you can actually see numerical readings on this bank) then something is up with the cat. Might take a second tank of gas to clear things up.