I have done the searches and know this is a common thread but cannot seem to find the answer to my problem. I have had an aftermarket header with test pipe for a while now and (for obvious reasons) gotten a P0420 code which is a post catalytic efficency code. I have just recently put in the oem cat for smog check and have driven about 30 miles but the code remains on and CEL/SES light is still on.

My question is will the sensors recognize the cat and automatically erase the code or do I have to have the code cleared for it to go off? I have a scangauge II but it wont reset the code which is no surpirse. So who out there has done this? Is it automatically reset or do I manually have to clear it? Smog is coming up soon so help is appreciated.

 

Well I figured it out...the lack of responses is comical. Readers tend to assume that a post similar to others does not contain any new information when in reality a poster may be seeking information to a question never asked or answered. To anyone in the future that may have this question the answer is simple. After putting the oem cat on my aftermarket header the SES light code P0420 would not shut off as it has in the past after about 30 miles or so. My scangauge would not reset it so I feared I would have to have a shop reset the code and hope it stayed off. What I ended up doing was cycling the ignition 5 times then after cycling it the light remained on but my scangauge was able to succesfully clear the code. It has stayed off now for about 200 miles and passed smog. So to get the code ready to reset the computer must see an active driving cycle. I am glad I didnt have to have it professionaly cleared.

 

lol. sorry! i would have been able to answer you on the first day if i had checked this section of the forums!

the ECU looks for problems every time you start the car. if the problem is "fixed", then just as you have seen, after 5 cycles it will self clear its codes.

as for resetting codes, take the car to auto-zone / pep boys. ask to use their code scanner. YOU are allowed to reset your cars codes, they are not. so just ask to use the programmer, and YOU have to hit the reset button.

Doesnt get any cheaper than FREE!

btw, have you thought about getting a hi-flow cat? ive also seen "O2 sensor spacers" for test pipes and hi flow cats, that set the sensor farther away from the center of the exhaust, causing the sensor to read the edges of the exhaust gasses, where it is slightly cooler, allowing you to run w/out a cat (possibly) or "safely" with a hi-flow cat.

 

BTW, is your header the 4-2-1, or just the 4-1 version?

ive read that there IS a difference in performance, and that the 4-1 is more for "racing" with higher power in the top end. VS the 4-2-1 which gives a more even power band for daily driving.

ive been wanting headers for some time now, and the Megans look the best value. What you think? thx

 

[/QUOTE]btw, have you thought about getting a hi-flow cat? ive also seen "O2 sensor spacers" for test pipes and hi flow cats, that set the sensor farther away from the center of the exhaust, causing the sensor to read the edges of the exhaust gasses, where it is slightly cooler, allowing you to run w/out a cat (possibly) or "safely" with a hi-flow cat.[/QUOTE]

I looked into some of the angled sensor bungs and spacers mentioned here on the site but couldnt really bring myself to test one. After talking to some mini techs and reading around it was brought to my attention that high flow cats and tuned minis with header upgrades do not always get along so I chose to stick with the oem cat which has proven to be one tough piece. When I installed my new header my cat was in working condition so I wasnt going to fix something that wasnt broke.

[/QUOTE]BTW, is your header the 4-2-1, or just the 4-1 version?

ive read that there IS a difference in performance, and that the 4-1 is more for "racing" with higher power in the top end. VS the 4-2-1 which gives a more even power band for daily driving.
ive been wanting headers for some time now, and the Megans look the best value. What you think? thx[/QUOTE]

I currently have the Megan Racing header which if I am correct is a 4-1 set up and I will admit you do lose a lot of your low end power and gain a hint of top end power if you choose to run with a test pipe. Also with a test pipe it tends to sound a bit "ricy" in the top end. I ran a year with a megan header w/test pipe, resonator delete, and invidia exhaust and the drone was honestly not too bad but at WOT it was extremely loud!!! Also with a test pipe and the P0420 SES on I noticed the vehicle ran rich and tended to feel bogged down and get bad mpg. With the megan header/oem cat, resonator delete,and invidia exhaust it sounds deep and tone rich and I love it.I will expres my love for this header because of its test pipe design. Unlike the oem manifold you can replace the cat/test pipe without having to replace the whole manifold which is just awesome and makes the switch from track days to daily driver just a matter of four bolts and switchingout a test pipe/cat.