I have an p0420 code have read it's probably catalytic converter bad.
How do I know for sure? Have taken temps on both and the closest one which I believe is bank 2 is about 100 degrees higher. Is thAt bank 2 and is this what to look for? Thanks for any help

 

This one has had 55 views but no answers. Let me stick my neck out and start the ball rolling for you.

P0420 : Catalytic converter system efficiency below threshold - bank 1

Possible Causes:
1. HO2 sensor disconnected
2. HO2 sensor to ECM wiring fault
3. HO2 sensor heater to ECM wiring fault
4. HO2 sensor heater failure
5. Upstream HO2 sensor failure
6. Downstream HO2 sensor failure
7. Catalyst failure

So the probability is HO2 sensor rather than Cat which has to be good news.

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Graham

 

Would the cat not be rattling and banging around if it was dead. i think your chances are one of the lambda's are dead. how ever lucky for you if its a front one as the rear ones are a pain to change.

 

jcarver, like was mentioned here, odds are, one of your O2 sensors is acting up. WIth our cars, the upstream sensor sees more abuse and therefore is your most likely culprit. The P0420 is a bank 1 error. So, if you look under the air box, you will see the sensor sticking out the side of the cat. So, remove the air box, use the appropriate size wrench and remove the O2 sensor. Then see what you have.

When you list your location is Washington, is that Washington DC or Washington State? If it is DC, I may be able to help you out some as I have a reader now that will list the O2 sensor voltages and we can confirm an issue. If you are in Washington State, I would recommend getting what is called an "ELM 327". It is a little device that plugs into your OBD socket under the dash. Then using a laptop or smart phone (via blue tooth), you can use a program called "Torque" to talk to the ELM unit and pull the desired data from the car. For the $10 it will cost you to get the ELM unit, it will pay for itself over and over just in gas saved running to the local auto parts store. I got the micro unit and just keep it in the glove box in case I need it or I want to help out a friend.

 

Thermo, I've been having the same issue's. I'm a bit confused and maybe you can clarify. The P0420 code is bank 1. I thought Bank 1 was the firewall side of the car? I have the downstream O2 sensor but was thinking I needed to figure out a way to get back there to change it (probably taking the upper intake off). But if bank 1 is the front near the radiator, that's a breeze! I'll just get the other sensor and change both. the car is bucking like crazy when under load on hills and such. the code that comes up all the time is the 420. It's also been giving me random miss fires and going into limp mode when it starts bucking. I plan on changing the plugs and putting new coils on it when I take off the intake. I think the plugs may be shot because after thinking the rear cat was bad, I did a battery of Seafoam, Cataclean and now this stuff from Autobarn. I'm trying everything before having to tackle that rear cat. but again, which is bank 1 and which is bank 2?

 

Joe, you are correct. I always seem to get the cylinder numbers mixed up (too many years of playing with the old Chevy's). Yes, bank 1 is against the fire wall, 2 is against the radiator.

As for your misfire issue, I would change the plugs and then see what you have.

 

Thermo,
Yea, that's going to be my next step. I'm hoping that with the continual run of cleaners that I ran, the plugs are probably shot. since I have it all apart again, I'm going to change the coils while I'm at it and hopefully get to the downstream o2 sensor in the back. thanks for the reply

 

Hi Joe, how did you make out with your misfire under load. I am having the same issue and was wondering how it worked out with you. I have changed 02 sensors, plugs, added 02 sensor extensions w/o any improvement. Thanks, Steve