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Old 03-18-2008, 02:45 PM   #1
WorldRallyX05
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Default How-To: DIY aftermarket Downpipe CEL fix

This is a do it yourself Check Engine Light (a.k.a. CEL) fix for the WRX for use after installing an aftermarket downpipe (a.k.a. DP) with either a high flow catalytic converter or no catalytic converter (a.k.a. Cat) at all and you are getting a cat efficiency code.

If you already know how to do this, or you have seen similar threads, then that's awesome, just don't reply to my thread saying, "There is already info on this out there" or "you just need to do a search and figure it out". I did both of these and figured it out myself. I just don't think that if someone wants to do this exact same mod, they have to search and piece together information from different threads. This is a specific how-to article for this exact mod only... the information has been pre-pieced together for you.

Ok... the idea behind this fix is to basically confuse... well, actually, not confuse... trick is a better word... trick your car. By pulling the O2 sensor out of the direct flow of exhaust and isolating it inside its own little space confuses the car into thinking that the air coming through your new catted or catless DP is clean.

This fix in this thread was performed on a Catted Helix Downpipe on my 2005 WRX sedan.

Ok... so first of all, this is what you will need for this fix.

1. Two 18mm spark plug non-foulers (a.k.a. anti-foulers). I bought the "HELP!" brand (part #42002) at my local pepboys, however they can be found at many auto parts store out there. Cost: $4.50

2. A 1/2 inch drill bit. Cost: $12.50

3. Access to a power drill or drill press

4. A vise... a table vise, bench vise, workshop vise, whatever you want to call it. You just need one.



Alright... here we go.

Step 1. Raise the front of your car up on jacks. Remember: When putting your car up on jacks to always be on a level surface and firmly set your parking brake.

Step 2. If the sensor hole in your exhaust is already unplugged, great! If it's not, Unscrew the plug from the rear sensor opening in the rear section of your new downpipe as seen below. If you didn't remove the oxygen sensor from your car during your DP installation then cut the zip ties that are holding the cable down and unplug it. Once it has been removed from the car you can wipe off all the old exhast dust from the sensor with a dry towel. Set it aside for now.



Step 3. Take one of your spark plug non foulers and drill a 1/2 inch hole through it to make clearance for the O2 sensor to fit inside it. This can be done with a power drill and a vise... the metal is relatively soft. See before and after below:



Step 4. What you are going to do now is screw the oxygen sensor in the non fouler you just drilled and then into the non fouler that you have not drilled... like so:





Step 5. Put this setup into a vise and tighten down both connections with a 22mm wrench.


Step 6. Screw this whole setup into the rear hole of your downpipe. Screw it in there pretty tight as you don't want any exhaust leaks.



Step 7. Plug it back into the black female O2 sensor cable found on the drivers side.

Step 8. If your wrx already threw a CEL at you, then you need to reset your ecu. To do this all you need to do is grab a 10mm socket or wrench and disconnect the negative end of your battery. Depress the brake for roughly 5-10 seconds (i have never needed to depress the brake any longer than this in order to drain the leftover charge flowing through my car) and then reconnect the battery.

Enjoy your clean instrument panel!

I'm not a professional auto mechanic, so If I have misinterpreted anything or explained anything incorrectly, then please PM me with any contradicting references that you have come across and I'll fix it pronto.

I have always used forums for "how-to" articles and I have never made one, so I felt it was time to start giving back! I hope this is a good start.
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Last edited by WorldRallyX05; 04-23-2008 at 04:54 PM.
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Old 03-18-2008, 03:13 PM   #2
hella_sti
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nice write up, but didn't someone already have a few pages on this mod?
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Old 03-18-2008, 03:30 PM   #3
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Old 03-18-2008, 03:36 PM   #4
dave_88
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Nice. Even though there is a thread already, this is easier for a noob to follow; instead of sifting through all those pages
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Old 03-18-2008, 07:13 PM   #5
WorldRallyX05
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Quote:
Originally Posted by Feign View Post
Yeah, i saw that, but this fix is a lot better for a few reasons:
1. It is way easier.
2. It fits better.
3. It looks a lot cleaner.
4. You don't need to weld anything.
5. The parts are cheaper.

If you have a welder (like Macabre, the person who posted the referenced link above) then i guess you could do it that way, but i have access to a mig welder, and I decided to do it this way because of the above reasons. I dunno ... a lot of these DIYs are subjective, but the point is... that this one works and its cheap.
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Old 03-19-2008, 01:16 AM   #6
jack klompus
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good write up. Ive been doing this mod exactly as you write it for 3 cars now with no CEL's.
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Old 03-19-2008, 08:45 AM   #7
Feign
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Quote:
Originally Posted by WorldRallyX05 View Post
Yeah, i saw that, but this fix is a lot better for a few reasons:
1. It is way easier.
2. It fits better.
3. It looks a lot cleaner.
4. You don't need to weld anything.
5. The parts are cheaper.

If you have a welder (like Macabre, the person who posted the referenced link above) then i guess you could do it that way, but i have access to a mig welder, and I decided to do it this way because of the above reasons. I dunno ... a lot of these DIYs are subjective, but the point is... that this one works and its cheap.
Yeah, but the anti-foulers are mentioned in there.

I'm not going to knock this thread, but I found out how to do this with a little bit of searching (back when the search sucked balls, mind you) and a little bit of brain matter to piece information together.
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Old 03-19-2008, 12:21 PM   #8
WorldRallyX05
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Unhappy i don't get it

Quote:
Originally Posted by Feign View Post
Yeah, but the anti-foulers are mentioned in there.

I'm not going to knock this thread, but I found out how to do this with a little bit of searching (back when the search sucked balls, mind you) and a little bit of brain matter to piece information together.
How do you think i figured it out? Just the same way you said you figured it out; "with a little bit of searching and a little bit of brain matter" I'm helping out the people who constantly search for this without finding one conclusive thread. I thought i would make it easier for some people so that they wouldn't have to search all over the place and piece together threads like you said, just to figure out something as simple as this.

I don't understand what is with people... I took time out of my day to go back and take pictures of what i had done earlier that day to help people out there who had the same problem i did, and I keep getting people who are saying i didn't need to post it. Well, there are thousands and thousands of threads that aren't of use to EVERYONE out there, but there are definitely some people out there who really need them, so if this thread is of no need to you as an individual, then don't say anything unless its a complement, and move on with your day. I can guarantee you that at one point or another, sombody (hopefully more than just a somebody) will find this thread and use it just the way it was designed to be used. As a HOW-TO, not a target for criticism.

If you already know HOW TO do this, then you have no business reading it, or wasting your time commenting on it.

Sorry if this thread bothers anyone, but i made it because i couldn't find one like this when i wanted to do this same thing to my car, so i did it to help out those who are in the same situation. So, if you're not in said situation, and you're not leaving a complement (BTW, thanks for the complements from everone!) then i don't know why you're leaving a comment.

SO, that having been said, lets try and save the criticism for things a little more important than how-to threads that you already understand and have figured out for yourself.

The only criticism that i want, and that i have previously stated in the original post, is if i have misinterpreted anything or explained anything incorrectly. I know that there are other threads out there that contain similar information, that is how i figured it out for myself, but if one person pieces together all the information regarding one issue and puts it all together in one thread, that will save a lot of people a lot of time in the future.
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Old 03-19-2008, 02:04 PM   #9
WorldRallyX05
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Quote:
Originally Posted by dave_88 View Post
Nice. Even though there is a thread already, this is easier for a noob to follow; instead of sifting through all those pages
Thanks!!! That is my thinking exactly.


Quote:
Originally Posted by fubarud View Post
good write up. Ive been doing this mod exactly as you write it for 3 cars now with no CEL's.
Thank you! Nice... it's good to hear its a reliable fix.
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Old 03-20-2008, 12:10 AM   #10
Feign
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Quote:
Originally Posted by WorldRallyX05 View Post
I thought i would make it easier for some people so that they wouldn't have to search all over the place and piece together threads like you said, just to figure out something as simple as this.
I thought that was what the search function was for?

Quote:
I don't understand what is with people... I took time out of my day to go back and take pictures of what i had done earlier that day to help people out there who had the same problem i did, and I keep getting people who are saying i didn't need to post it. Well, there are thousands and thousands of threads that aren't of use to EVERYONE out there, but there are definitely some people out there who really need them, so if this thread is of no need to you as an individual, then don't say anything unless its a complement, and move on with your day. I can guarantee you that at one point or another, sombody (hopefully more than just a somebody) will find this thread and use it just the way it was designed to be used. As a HOW-TO, not a target for criticism.

If you already know HOW TO do this, then you have no business reading it, or wasting your time commenting on it.

Sorry if this thread bothers anyone, but i made it because i couldn't find one like this when i wanted to do this same thing to my car, so i did it to help out those who are in the same situation. So, if you're not in said situation, and you're not leaving a complement (BTW, thanks for the complements from everone!) then i don't know why you're leaving a comment.
Most everyone that runs a catless downpipe is intelligent enough to discover at least one of the two fixes for this particular CEL.

Quote:
SO, that having been said, lets try and save the criticism for things a little more important than how-to threads that you already understand and have figured out for yourself.

The only criticism that i want, and that i have previously stated in the original post, is if i have misinterpreted anything or explained anything incorrectly. I know that there are other threads out there that contain similar information, that is how i figured it out for myself, but if one person pieces together all the information regarding one issue and puts it all together in one thread, that will save a lot of people a lot of time in the future.
Yes, thank you. I said it was a good thread, but you should not expect any nut-fluffing.
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Old 03-20-2008, 02:16 AM   #11
WorldRallyX05
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Quote:
Originally Posted by Feign View Post
Yes, thank you. I said it was a good thread, but you should not expect any nut-fluffing.
I never expected that, nor did i say that i expected it.
Thanks for saying it was a good thread, but it doesn't mean much when you follow it up right away with "... BUT, I found out how to do this with a little bit of searching". So what... a ton of people just like you found out how to do it with a little bit of searching, including me... I don't really care that you found it with a little searching. I obviously didn't make the thread for people like you who already know how to do this, so leave it alone. You're commenting on a thread that obviously doesn't concern you sine you already know how to do it, so just drop it. I don't understand why a comment like "I found out how to do this with a little bit of searching (back when the search sucked balls, mind you) and a little bit of brain matter to piece information together" is even warranted. Are you trying to say that my thread is of no use to this community? because i assure you, it will be used. I'm not the only person who has recently done this to his/her car.

If you really feel that this thread doesn't belong... then take it up with a moderator and quit scrutinizing my thread.
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Old 03-20-2008, 11:27 PM   #12
Ioku
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Nice write up but do you know if this would work for an N/A car to, I was thinking of gutting my cats but didn't want to get any cels so if this could work for N/A's too that would be great.
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Old 03-22-2008, 09:25 PM   #13
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Great write up man! Much easier to follow that those other ones.

Those of you knocking it.... Shuuuuuut uuuuuup. It's simple and to the point.
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Old 03-22-2008, 09:54 PM   #14
WorldRallyX05
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Quote:
Originally Posted by WRX_WGN View Post
Great write up man! Much easier to follow that those other ones.

Those of you knocking it.... Shuuuuuut uuuuuup. It's simple and to the point.
Thanks man, thats exactly what i was trying to do!... i appreciate the complement.
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Old 03-23-2008, 05:15 AM   #15
kike_ej20
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Quote:
Originally Posted by WorldRallyX05 View Post
Thanks man, thats exactly what i was trying to do!... i appreciate the complement.
Man, don't sweat it,people criticize everything You did a great job plus it has pictures and everybody loves that when they are trying to do something themselves
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Old 04-02-2008, 01:29 PM   #16
07SPTWRX
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nice - i did the same thing on my civic when i went to a cat-less system.
the only thing i think is missing, is what size non-fouler to use. I know from when i did my civic there were 3 or 4 diff sizes.

other than that - good job
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Old 04-02-2008, 02:54 PM   #17
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Quote:
Originally Posted by 07SPTWRX View Post
nice - i did the same thing on my civic when i went to a cat-less system.
the only thing i think is missing, is what size non-fouler to use. I know from when i did my civic there were 3 or 4 diff sizes.

other than that - good job
Whoops.... sorry about that, they're 18mm, I'll go add that in. Thanks!
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Old 04-14-2008, 02:09 AM   #18
captureandrelease
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Thank you very much, this is very helpful. Feign is bored and is a douche.
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Old 04-14-2008, 10:42 AM   #19
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This thread actually helped me...I wasn't sure if I wanted to go with a catless downpipe b/c of the CEL, but now it's clear that's the direction I'm going to go. Plus, I don't have a clue on how to weld.

Thanks for the write-up.
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Old 04-22-2008, 11:53 AM   #20
BriGuy
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I did this fix, but it didn't really work for me. After about 3 days of driving, my check engine light came on again. When I look up the code in my accessport, it comes up as no code found. This has always been ever since I went catless. I have a turbo XS downpipe and Perrin catback on an 06 sti... any suggestions????
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Old 04-22-2008, 11:33 PM   #21
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Great write up. We need more write up with pictures.
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Old 04-23-2008, 04:53 PM   #22
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Thank you to all!!!
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Old 04-24-2008, 11:08 PM   #23
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Nice write up. Thanks.
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Old 04-30-2008, 01:01 AM   #24
unclben7
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I wish I would have known about that before I bought the cel fix online which is exactly what you did, but it included the resistor as well...I would have saved a bunch of money. Good job!
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Old 04-30-2008, 01:23 PM   #25
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Do you think that I would be able to pass NY inspections if I did this to all my sensors? I have a complete catless turboback.
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