Catless CEL Fix

A

arkenzo

Banned
If you're running a catless exhaust (heaven forbid), you might have a check engine light (CEL), to remedy this problem, disconnect your secondary o2 sensor #2, completely remove it and while you're at it, unplug your negative battery terminal cable (reset the ecu).

After you remove the secondary o2 sensor #2, cut the black sleeve in the middle with a razor blade, then cut the black wire wherever you desire (strip some of the black wire ends to allow proper connection to the butt connectors).

crimp the butt connectors on each ends of the black wire, make sure to tug on them to make sure they're properly crimped. Afterwards, time the rectifier diode to your desire specifications, then crimp both ends of the diode to your existing (already connected) butt connectors, tug on them to make sure they're properly crimped. Safely secure your connections with electrical tape and or heatshrink tubing. You're done, now connect the negative battery terminal to it's post, plug in your secondary o2 sensor #2.

The below pictures will help you analyze this project.

cel1.jpg

cel2.jpg


By the way, the non-fouler trick doesn't work on a completely catless exhaust (no)
 
would you like to put a wager on that statement? lol

I've been running completely catless and w/ the nonfouler for about 4 years with 0 CELs...
arkenzo said:
If you're running a catless exhaust (heaven forbid), you might have a check engine light (CEL), to remedy this problem, disconnect your secondary o2 sensor #2, completely remove it and while you're at it, unplug your negative battery terminal cable (reset the ecu).

After you remove the secondary o2 sensor #2, cut the black sleeve in the middle with a razor blade, then cut the black wire wherever you desire (strip some of the black wire ends to allow proper connection to the butt connectors).

crimp the butt connectors on each ends of the black wire, make sure to tug on them to make sure they're properly crimped. Afterwards, time the rectifier diode to your desire specifications, then crimp both ends of the diode to your existing (already connected) butt connectors, tug on them to make sure they're properly crimped. Safely secure your connections with electrical tape and or heatshrink tubing. You're done, now connect the negative battery terminal to it's post, plug in your secondary o2 sensor #2.

The below pictures will help you analyze this project.

cel1.jpg

cel2.jpg


By the way, the non-fouler trick doesn't work on a completely catless exhaust (no)
Click to expand...
 
well I'm just saying, according to your statement then mine shouldnt work either...

Is this proven that the nonfouler wont work on the MS3?
arkenzo said:
This fix is for the Mazdaspeed 3, not your Mazda Protege, okay? Thanks (fuoops)
Click to expand...
 
evilmonkeyMSP said:
well I'm just saying, according to your statement then mine shouldnt work either...
Click to expand...

Dude, my statement is in regards to the Mazda3/Mazdaspeed3, which is why It's in this specific forum, I am in no way relating any of what I have posted, to your Protege....How hard is it to comprehend this ??? (chair)
 
lol I'm just ****** with you either way lol But I had no idea the non fouler didnt work for the MS3....weirdness, works for most others... (crazy)
 
evilmonkeyMSP said:
lol I'm just ****** with you either way lol But I had no idea the non fouler didnt work for the MS3....weirdness, works for most others... (crazy)
Click to expand...

Not sure why it didn't work for my 2008.5 or my friends 2007, but we've tried so many different combinations, 1 non-fouler, then 2, then 3, then 4 (boom04) but none of them worked for more than 200 miles, so I read up on that audi tech guy's article and it made sense about the voltage relations to the secondary o2 sensor and how the secondary o2 sensor sends a different voltage to the ecu due to a catless setup. This method worked best for me, maybe the non-fouler will work ok for 1 cat setups, not sure. so please don't lay the ban hammer on me (bow)...............(nervous)
 
odd (boom07)

On my set up I have 1 nonfouler drilled out to a 1/2 inch that goes into another non fouler and then that goes into the O2 bung... Tried that setup yet?

lol im not banning anyone, quit being a tard lol
 
Running catless with non fouler AND a CEL. I reeeeeeeeeeeeally don't want to hack up my O2 sensor wiring. Anyone have any other tips, tricks, or methods for getting the CEL off?
 
lestat13 said:
Running catless with non fouler AND a CEL. I reeeeeeeeeeeeally don't want to hack up my O2 sensor wiring. Anyone have any other tips, tricks, or methods for getting the CEL off?
Click to expand...

You can always revert back to stock, you're simply splicing into a wire....If you ever need to revert back to stock, just remove the diode, crimp the black wire back together or solder it back together and that's it....
 
you could also buy a secondary o2 sensor although idk if it comes with the wire you need to cut. it's not nearly as expensive as the primary o2 sensor though
 
I really hate to awaken such an old thread but can anyone explain why using a diode to create a voltage drop works better than a resistor in this situation?
 
I don't know, you'd think they would work the same... My cel code I've had since this summer when I put my catless dp reads that my cat has failed to warm up, thats what the code reads.... so changing the voltage so that the sensor thinks it is reading the correct heat temp setting makes sense... I was going to just put my stock dp back in here in a little bit to pass s/e, but if this actually works I might do it...
 
Last edited:
RichB said:
I really hate to awaken such an old thread but can anyone explain why using a diode to create a voltage drop works better than a resistor in this situation?
Click to expand...

Because a diode creates a voltage drop regardless of load? The signal is probably tied to a high-impedance input already. Just guessing...
 
Man, I had no luck getting the O2 sensor out. I had to put the diode in with the sensor still installed. Lets see if it holds up.
 
Its been a few weeks and I have been checking my codes after every trip and have had nothing. This fix works like a charm!
 
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