[67stangman]

Just recently started getting a P0420 code. It started right after I changed over from 87 to 93. I did this because I will be getting a 93 tune in the near future. I know the tune will shut off these codes but I was curious as which sensor could be mal-functioning assuming my cats are ok. They are Steeda high flows with about 35K on them. I reset the code but it comes back around 150 miles of driving.

P0420 translates to Bank 1 but I can't tell if its upstream or downstream. I was told its probably the cat because the high flows don't last that long. Any possibility the change over in octane caused the problem, or is it just a coinencidence?

[CobraBoy]

P0420 Catalyst System Efficiency below Limit - Bank No 1.

there is your answer to your problem....

[markwondi]

Originally Posted by CobraBoy

P0420 Catalyst System Efficiency below Limit - Bank No 1.

there is your answer to your problem....

LOL, nice answer.


Bank 1 is passenger side, and since the code is a catalyst code, it would be your rear o2 sensor.

[67stangman]

Originally Posted by markwondi

LOL, nice answer.


Bank 1 is passenger side, and since the code is a catalyst code, it would be your rear o2 sensor.

Thanks for narrowing it down. I figured as much but wanted to be sure. Its probably the cat anyway.

[67stangman]

Originally Posted by markwondi

LOL, nice answer.


Bank 1 is passenger side, and since the code is a catalyst code, it would be your rear o2 sensor.

Should have asked this before, but if it turns out the cat is bad, should I replace it before the tune? Will it affect the perfomance tune at all?

[BlueStreak03]

Yeah go ahead and replace it as soon as you can. A bad cat can wreak all kinds of havoc on the car, not to mention the horrible smell that'll follow you everywhere as it gets worse.

[67stangman]

Originally Posted by BlueStreak03

Yeah go ahead and replace it as soon as you can. A bad cat can wreak all kinds of havoc on the car, not to mention the horrible smell that'll follow you everywhere as it gets worse.

I wrote to Steeda tech support so hopefully they will get back to me. Someone told me they (high flow cats) don't last long but I think they should last longer than 35K miles, but I don't know. If they respond, I will point it here for what its worth.

[reivaxtorres]

Originally Posted by 67stangman

I wrote to Steeda tech support so hopefully they will get back to me. Someone told me they (high flow cats) don't last long but I think they should last longer than 35K miles, but I don't know. If they respond, I will point it here for what its worth.

for what its worth, ive had the bbk hi-flow cats on my car since about 96k or 98k miles, and im creeping up on 157500 miles on my car and the cats are still working perfect as of july (got it tested). ill know again in jan if the cats are still working or not as i need to get it smogged again.

[67stangman]

Originally Posted by reivaxtorres

for what its worth, ive had the bbk hi-flow cats on my car since about 96k or 98k miles, and im creeping up on 157500 miles on my car and the cats are still working perfect as of july (got it tested). ill know again in jan if the cats are still working or not as i need to get it smogged again.

I am sure a lot of it has to do with driving habits and particularly gas that you buy but I figure they should go a minimum of 50K or better or who would by them. I am sure stock ones last 3 x that.

[reivaxtorres]

Originally Posted by 67stangman

I am sure a lot of it has to do with driving habits and particularly gas that you buy but I figure they should go a minimum of 50K or better or who would by them. I am sure stock ones last 3 x that.

yeah, gas quality and engine management is what really dictates the life of the cats. if your car runs rich (mine does), then the cats have a shorter life because it has more to try to clean up. im not too sure if driving habits have anything to do with it tho.

[aacuna]

Originally Posted by reivaxtorres

yeah, gas quality and engine management is what really dictates the life of the cats. if your car runs rich (mine does), then the cats have a shorter life because it has more to try to clean up. im not too sure if driving habits have anything to do with it tho.

Why is ur car runing rich

[reivaxtorres]

i really have no idea, everytime ive smogged it ive noticed its on the rich side, and so far ive only been able to blame it on either the old o2 sensors i had (recently got new ones), dirty MAF, or the SVO fuel pump i have. it doesnt run too rich, and its mostly only at idle and low RPMs.

[steve_stang2003]

Originally Posted by 67stangman

Just recently started getting a P0420 code. It started right after I changed over from 87 to 93. I did this because I will be getting a 93 tune in the near future. I know the tune will shut off these codes but I was curious as which sensor could be mal-functioning assuming my cats are ok. They are Steeda high flows with about 35K on them. I reset the code but it comes back around 150 miles of driving.

P0420 translates to Bank 1 but I can't tell if its upstream or downstream. I was told its probably the cat because the high flows don't last that long. Any possibility the change over in octane caused the problem, or is it just a coinencidence?

Just went through this on my daughter's 2003 Jetta.
Clear the code and it comes back about 200 miles later.
It's most likely not the sensor, but the cat that is not working correctly. The sensor is doing it's job letting you know this.

VW replaced the cat for free under the 80k mile emissions warranty.