P0420 code

Just bought my WS6 with only 10,000 miles, and on the trip home I get a check engine light. The code is P0420 -- Catalytic efficiency below threshold (Bank 1). I already took it to my local shop, and had the Pontiac dealer look at it. Both said almost immediately that I would need a new catalytic converter. My question for the list experts is which O2 sensor is bank 1? Is it driver's side, or passenger side? I figure it only makes sense to check the sensor before letting them dick up my exhaust system.

Bank 1 is the drivers side and the post cat sensor is sensor 2.

There's also a federal emissions warranty that's good up to 80,000mi...but that doesn't matter because you only have 10,000mi on the clock and GM extended the cat warranty to 120,000mi.:yay: The pontiac dealer should've replaced it right there on the spot...I dunno why they didn't unless they're just being pricks.

Thanks for the info... Any chance it's just a bad O2 sensor? Seems pretty strange the cat would go bad after only 10k miles...

Yea it's possible...try swapping the driver side o2 with the passenger side...if you get a p0430 code (passenger side low efficency code) you know it's the o2.

I'd let the dealer figure it out. New cat + labor = free ( http://www.ls1.com/forums/showthread.php?t=35957 ). If that doesn't fix it, then you'll know it's the sensor. The cats on these cars have been known to fail anywhere from 5k-130k miles. Could very well be the problem. I wouldn't waste my time.

my wife's 2001 firebird is throwing a 420 code also. it has 84,000 miles and i changed the cat. still throwing the code. i was wondering if you changed the o2 sensor, and if so, did that fix the problem? thanks, ryan.

GM extended the stock cat warranty on the LS1 00-02 F cars last December to 10 yrs/120K - even reimburse you if you had it replaced earlier. Rarely is P0420 the sensor if installed correctly and keeps coming back.

why would it come back then if i already changed the cat?

It won't go off immediately unless you clear it, assuming it's been changed for a while? Dunno. See www.gearchatter.com/viewtopic9138.php

it was changed on sept 1st. light was still on and i reset it by pulling the negative cable on the battery. this lasted for two days. light is back on now. this is a v6. i don't know if that makes a difference or not.

Go to Autozone and have them delete it with a handheld. I don't think removing the battery cable actually deletes a code on the OBDII system like it did the OBDI.

Just a thought. Did you replace the converter with an OBDII compatible one? Some of the cheaper ones don't do well and can set codes.

i bought the one autozone's computer said was for the car. although it was not the most expensive one. i just had autozone reset the light. we'll see if it comes back. thanks for the help.