Check Engine light

I have a 2001 grand prix gt 3.8 n/s. The check engine light comes one its for a oxygen sensor bank 1 code. I replaced it and it went off every other day it comes back on. I purchased a new IACV, MASS air flwo (they both needed it ). car runs great but the light comes on i turn it off and it comes back on. I did just have the converter replaced about 6,000 miles ago could that have anythign to do with it.

When the light comes on, has it been the bank 1 O2 sensor every single time or are there any other codes at all?

WHat is the specific code that pops up?

P0420?

yes p0420 is the code. Thats the only one that comes on. It came on again today i shut it off drove home about 20-25 miles and it kicked back on. I called the shop they told me there was no way the cat was bad since it is only 3 months old. ANy ideas

P0420 Catalyst System Efficiency Below Threshold

This indicates the difference between the readings from the pre and post cat oxygen sensors is below what the PCM's programming indicates it should be.

This could be caused by a few different issues.

1. You had a cheap universal weld-in converter installed and it isn't efficient enough to meet OEM specs
2. Your new upstream oxygen sensor is junk (Bosch brand by chance?)
3. Your post cat oxygen sensor is carboned up, and no longer able to match the new upstream sensor's performance, thus tripping the P0420 code, but not bad enough to trip a post-cat sensor code.

There are other variables that could cause this condition as well, but these 3 are the most likely.

okay. Know what kind of oxygen sensor should i get and if i dont change it right away what is the drivability of the car. My question what does a bad oxygen sensor do besides hurt the gas millage and eventually the CAT.

It is more expensive but get the GM brand. You will be better off usually with a GM part over a non GM part.

I agree with Doc, get an AC-Delco to avoid all the possible aftermarket junk hassles.

X3, I've had so many issues with aftermarket junk. However GM quality has been questionable recently also.

X3, I've had so many issues with aftermarket junk. However GM quality has been questionable recently also.

I agree. I think it really is a part-by-part play when you are trying to determine GM quality vs. aftermarket.