I have a 2001 monte SS. I went to get a smog test today and I failed. Last week my check engine light came on. The smog guy told me this was the error code P0420 Cat Efficiency Below Threshold. Does anybody know what I need to get repaired on the monte? The smog guy said all I need is a new censor on the catalytic converter. Does that sound right?

Thanks in advance.

 

I looked at the smog report closely, and looks like everything passed except for the fact that my check engine light was on. I'm thinking I should just reset the code using a Code Reader. What do you guys think?

 

Sounds like you might need a new O2 sensor, but how's it running? Have you ever had the catalytic converter replaced? I would guess that it's the cat' over the sensor, knowing the history of the problems with cat' failure.

 

Its running fine, just as always. I never had the cat replaced. I put in Borla mufflers 5 years ago, thats about it. I remember I had to reset that check engine light then too.

Judging from the smog report, it doesnt look like anything is wrong. Would it hurt to just reset the code?

 

i would replace the o2 sensor after the cat and go from there my truck and couger did the same after i went with a better exaughst. the new sensor will run better than the old one the old one is still used to the restrickted type of exaughst

 

Alright, I'll look into it. I just ordered a Code Reader anyways, just to try the reset. Worst case the check engine light will come back on right?

 

I decided to have the mechanic change the o2 censor. Anything else I should worry about?

 

Should I try putting a cheeseburger into the gas hole?

Will that make it work?

 

If you still don't pass after changing the O2 sensor, I would say your cat needs to be replaced. These cats are known to go bad.

 

But if he does a cat replacement (for a high-flow) he'll still have that light more chances than not :P