Service Code P0420, Bad Cat. Or Bad 02 Sensor?

[Green01]

I have a 2001 Sierra with a 4.8. It has been setting this code (P0420) off and on for about 60k mi. Some times it will not set the code for 10k mi. but then it will set the code every 100 mi. or so. I was told that a cat. was not bad until it started to break down inside. Should I try a new sensor or bite the $900 bullet and get a new cat? It needs to be smogged by the first of Feb. Here in Ca. the cat. has to be C.A.R.B. approved and it costs over $900.

Any help will be greatly appreciated.

[gmtech4]

told by who?

 

tisk tisk,waiting to the last minute to get it fixed,

[txab]

I have a 2001 Sierra with a 4.8. It has been setting this code (P0420) off and on for about 60k mi. Some times it will not set the code for 10k mi. but then it will set the code every 100 mi. or so. I was told that a cat. was not bad until it started to break down inside. Should I try a new sensor or bite the $900 bullet and get a new cat? It needs to be smogged by the first of Feb. Here in Ca. the cat. has to be C.A.R.B. approved and it costs over $900.

Any help will be greatly appreciated.

 

A cat can go bad without it rattling. What your O2 sensors are measuring the efficiency of the cats performance once it drops below a certain level you start getting the code. Sucks to be you in Ca.

[Green01]

told by who?

 

tisk tisk,waiting to the last minute to get it fixed,

 

Well, that was useful. tisk tisk

[Nytemare]

If your exhaust smells like rotten eggs...or fart...than you have a bad cat....if it doesn't....than chances are you have a bad O2 sensor....or 4

 

 

and there are way cheaper cats than 900 bucks that are CARB approved. MSRP for a Magnaflow one is 520...so on Amazon.com or something similar they should be way less.

[Green01]

If your exhaust smells like rotten eggs...or fart...than you have a bad cat....if it doesn't....than chances are you have a bad O2 sensor....or 4

 

 

and there are way cheaper cats than 900 bucks that are CARB approved. MSRP for a Magnaflow one is 520...so on Amazon.com or something similar they should be way less.

 

Nope, no eggs or farts. I will try the sensor and if it sets the code again I will get the Magnaflow. Thanks for the tip on the Magnaflow. The only time it sucked to be me was when I last visited my inlaws in TEXAS.

[Green01]

Oh yeah,, tisk tisk

[Nytemare]

Oh yeah,, tisk tisk

you have 4 post and 2 of them are bitching....you havent earned the right to be an a**hole yet.

 

And your welcome for the Magnaflow ones...you can probably get two of them for around 500 on most online parts places.

And if there's no smell...your probably looking at O2 sensors than. have the sensors activity checked at a shop that uses a tech II or similar diagnostic device. No use wasting your money on either if it is not the problem.

[txab]

If your exhaust smells like rotten eggs...or fart...than you have a bad cat....if it doesn't....than chances are you have a bad O2 sensor....or 4

 

 

and there are way cheaper cats than 900 bucks that are CARB approved. MSRP for a Magnaflow one is 520...so on Amazon.com or something similar they should be way less.

 

Nope, no eggs or farts. I will try the sensor and if it sets the code again I will get the Magnaflow. Thanks for the tip on the Magnaflow. The only time it sucked to be me was when I last visited my inlaws in TEXAS.

 

 

Hmmm, guess you like being bent over on emission stuff in Ca. then. The cost is what I was referencing. Have a good one.

[Green01]

If your exhaust smells like rotten eggs...or fart...than you have a bad cat....if it doesn't....than chances are you have a bad O2 sensor....or 4

 

 

and there are way cheaper cats than 900 bucks that are CARB approved. MSRP for a Magnaflow one is 520...so on Amazon.com or something similar they should be way less.

 

Nope, no eggs or farts. I will try the sensor and if it sets the code again I will get the Magnaflow. Thanks for the tip on the Magnaflow. The only time it sucked to be me was when I last visited my inlaws in TEXAS.

 

 

Hmmm, guess you like being bent over on emission stuff in Ca. then. The cost is what I was referencing. Have a good one.

 

 

Oooops, no bitching intended. I hang around with a bunch of knuckleheads that drink too much beer and shower once a week, but only if they really need it. We are constantly poking a stick in each others cages. These forums all look the same and without faces and a little history its easy to forget that you are not with the same bunch of friends.

 

Hope you all have a great new year.

[txab]

 

Tell us how things turn out for you.

[Nytemare]

If your exhaust smells like rotten eggs...or fart...than you have a bad cat....if it doesn't....than chances are you have a bad O2 sensor....or 4

 

 

and there are way cheaper cats than 900 bucks that are CARB approved. MSRP for a Magnaflow one is 520...so on Amazon.com or something similar they should be way less.

 

Nope, no eggs or farts. I will try the sensor and if it sets the code again I will get the Magnaflow. Thanks for the tip on the Magnaflow. The only time it sucked to be me was when I last visited my inlaws in TEXAS.

 

 

Hmmm, guess you like being bent over on emission stuff in Ca. then. The cost is what I was referencing. Have a good one.

 

 

Oooops, no bitching intended. I hang around with a bunch of knuckleheads that drink too much beer and shower once a week, but only if they really need it. We are constantly poking a stick in each others cages. These forums all look the same and without faces and a little history its easy to forget that you are not with the same bunch of friends.

 

Hope you all have a great new year.

 

No worries man...I'm pretty sure we were all joking around too....