Emission test failed...HELP

[Pejacob97]

So i needed to get my car reinspected since its been in the garage being fixed and is out of date by a couple months now, so i went to go take it to get inspected. Ends up i failed with the fail code of :

P0420: Catalyst System Efficiency Below Threshold (Bank 1)

I did some minor research on it, and i was told that it could be 1 o f 2 things, my cat is bad or my o2 sensors r bad. Well on the inspection report my 02 sensors came back as "Ready" so i assumed it wasnt them. So i went and and had my whole cat replaced, i needed it anyways, it fixed a strange noise my car was making so its a plus no matter what. So thinking ide fixed it, went to go get it reinspected and it still failed for the same reason. Any know why i am failing?

Thanks,
Phil

[aceyx]

The code needs to be reset after you fix things.

[L84THSKY]

I was discussing this issue a few weeks ago. I had a "catalytic efficiency" code stored in my system. The CEL light didn't light, but the code was stored. The car had been recently inspected, and passed emissions. I figured it might be the O2 sensor too, so I just had the post cat sensor replaced. I'm not sure if there are more than one cat efficiency codes, have to read my Peake code table. If my code comes back, I will look for other causes, but for now, my CEL has never come on for the "cat efficiency" yet.

Some other people have made suggestions about any other causes, do some searching.

Originally Posted by Pejacob97

So i needed to get my car reinspected since its been in the garage being fixed and is out of date by a couple months now, so i went to go take it to get inspected. Ends up i failed with the fail code of :

P0420: Catalyst System Efficiency Below Threshold (Bank 1)

I did some minor research on it, and i was told that it could be 1 o f 2 things, my cat is bad or my o2 sensors r bad. Well on the inspection report my 02 sensors came back as "Ready" so i assumed it wasnt them. So i went and and had my whole cat replaced, i needed it anyways, it fixed a strange noise my car was making so its a plus no matter what. So thinking ide fixed it, went to go get it reinspected and it still failed for the same reason. Any know why i am failing?

Thanks,
Phil

[Pejacob97]

Originally Posted by aceyx

The code needs to be reset after you fix things.

how do i do that? still learning basics =)

[Timberwoof]

Woah, old thread. Even so, someone else might stumble across it as I did.

If you have an OBD2 diagnostic tool that told you the P0420 code, then it probably has a button that will clear the codes out of the OBD2 system's memory. So plug the little protocol droid in, read the codes, and press his reset button.