Cel: P0420

[whoadizzle]

I got a CEL on my way home from the D&B meet in Philly. Scared the **** out of me cause I was 3 hrs from home, so I drove it anyways and made it alright.

Anyways I went to Advanced Auto and scanned my car and got this error code: P0420 Catalyst Efficiency Below Threshold. No idea what it means but I asked the guy at Advanced and he said could be bad gas or something and said to erase it and see if it comes back. So i erased it and it hasn't come back yet (drove like 15 miles).

Any ideas what this means?? Or is there somehting I should do??

[alpha Q]

probably a bad cat/o2 sensors

[CalPencil]

get the sensors, because you'll need to replace both anyways when you're doing it. If it doesn't clear right away, take out your new sensors and put in your old. Then buy a new CAT.

***Using an old failing CAT with new sensors, will damage the new sensors.
******When buying a new CAT, you should always use brand new sensors.

So, sensors first = $200
Cat second = $500 - $1300

But replacing these parts and getting that P0420 code will most definitely increase your gas mileage to what you're getting now, so that's something to look forward to after finishing this job...even if it is a lot of money. I just got the job done, and not to mention your car will feel different too... it'll be running more balanced and more efficient.

[slidr]

Originally Posted by CalPencil

But replacing these parts and getting that P0420 code will most definitely increase your gas mileage to what you're getting now, so that's something to look forward to after finishing this job...even if it is a lot of money. I just got the job done, and not to mention your car will feel different too... it'll be running more balanced and more efficient.

That's all in your head because that code, the sensor, and the cat (unless it's damaged) will not affect performance or gas mileage.


For a cheap fix, try this...http://newcelica.org/forums/showthread.php?t=216641

You will most likely not pass emissions, but the light will not come back.

[CalPencil]

having bad oxygen sensors won't affect your performance? are you kidding? Do a little bit of research...you'll find out that the oxygen sensors will either send communicate properly or not, and then your ecu will either throw more or less gasoline into the mix.

[slidr]

Originally Posted by CalPencil

having bad oxygen sensors won't affect your performance? are you kidding? Do a little bit of research...you'll find out that the oxygen sensors will either send communicate properly or not, and then your ecu will either throw more or less gasoline into the mix.

Durrr, do you know why there are two of them?

You do the research moron. Only one O2 sensor affects the AF ratio.

[CalPencil]

Two, one to check the air before the cat...two, to check the efficiency of the cat.

[whoadizzle]

got my code back again...im still getting around 30 mpg but i dont know if i should replace something or not.

[clarionguy]

Thats the only code I pulled a few times... For me, it only pops on once in a while ... Only happened during long drives (> 200 Miles) ..