Car threw code P0420

[Slow FX]

Had TPiS headers, y-pipe, and cats installed way back in November. Everything went fine.

Last week had a horrible rattle from underneath the car. By the time I had it looked at two days later the rattle disappeared completely. Couldn't visibly see anything that feel off the car. Car ran fine.

Two days later while driving. Filled up with regular gas (belowing freezing temps here and not going full throttle anytime soon). Car throws a code. No loss in performance nor can I tell anything is out of the ordinary.

We reset the code tonight. Now if it comes back, I'm assuming that it would only be the sensor and not the cat since it's practically new. Would you all agree?

[PC PaiN]

Are you running the rear O2 sensors or are you running sims? The code may not be related to what I'm getting at though.

[Dr.Mario]

You might have to get sims...i have macs with the the cat y-pipe and it threw that code if i remember right. I put sims on it and its fine. Guess i should get an ory now huh :rotfl:

[renips]

Originally posted by Slow SS
Had TPiS headers, y-pipe, and cats installed way back in November. Everything went fine.

Last week had a horrible rattle from underneath the car. By the time I had it looked at two days later the rattle disappeared completely. Couldn't visibly see anything that feel off the car. Car ran fine.

Two days later while driving. Filled up with regular gas (belowing freezing temps here and not going full throttle anytime soon). Car throws a code. No loss in performance nor can I tell anything is out of the ordinary.

We reset the code tonight. Now if it comes back, I'm assuming that it would only be the sensor and not the cat since it's practically new. Would you all agree?

I just had a cat crap out with less than 15k on it. These things can suck big time.

[JandJsTA]

Being the setup is fairly new Slow I would wait and see what happens and if it returns go for the SiMs because I can't believe the cats would be fouled already ..... Phil sells em for 100 at Fasttoys :)

[Slow FX]

I've actually got the O2 extensions so the O2s are still in place.

So if it's an O2 sensor are you guys saying I should replace it with a sim instead of another O2 sensor?

[killer01ws6]

Originally posted by Slow SS
I've actually got the O2 extensions so the O2s are still in place.

So if it's an O2 sensor are you guys saying I should replace it with a sim instead of another O2 sensor?

Sometimes on different setups, the O2 sensor is not close enough to read as it should, and the reading are off, in these cases you need to use a SIM, and keep your rear O2s for replacements they are the same as the frounts

[PC PaiN]

Originally posted by Slow SS
I've actually got the O2 extensions so the O2s are still in place.

So if it's an O2 sensor are you guys saying I should replace it with a sim instead of another O2 sensor?

If you are running the rear O2's still then that is your problem. When you change the cat and position of the cat you are changing how that thing will read. By running the rear O2's still you are more than likely always gonna set a code. I picked up a set of 02 sims for 50$ off a member of the board.

Also instead of getting O2 sims you can always have the rear O2's turned off via LS1Edit

[Slow FX]

Okay, so when I buy sims will I be replacing my front O2s or my rear??

Also, I need to pass emissions next month. Will this be a problem?

[PC PaiN]

Originally posted by Slow SS
Okay, so when I buy sims will I be replacing my front O2s or my rear??

Also, I need to pass emissions next month. Will this be a problem?

If you read my reply I said rear O2's :) It shouldn't be a problem as long as you aren't throwing any codes.

[Slow FX]

Originally posted by BlackWS602
If you read my reply I said rear O2's :) It shouldn't be a problem as long as you aren't throwing any codes.

So you're saying that I should replace my driver's side rear O2 with a sim and that should get rid of my P0420?

And it will also pass emissions after that?

[killer01ws6]

You should be ok for emissions with cats and no codes.

[Slow FX]

I did a search on another board and found a post by somebody that said he saw an exhaust leak cause the same code I got. He said on decelleration air would enter the system and throw the code.

Is it feasible to say that the rattling that disappeared could have been a peice of my exhaust that has left a leak?? Before the code I did notice that the car sounded louder but I wrote it off to my imagination.

What do you guys this of this theory?