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Downpipes & CEL - Any solution to PERMANENTLY remove/bypass CEL?

Seth

Seasoned Member
Joined
Feb 24, 2022
Messages
468
Location
Austin, TX
V-Series Cadillac(s)?
2022 CT4-V Blackwing 46-404
I know you can get the DTC Assassin but my understanding is that requires you to continually clear the CEL over time. I also know you can get the "EPA catted" but I do not want that.
Has anyone found a solution to permanently avoid CEL w./ downpipes?
 
They make o2 sensor spacers that trick the rear sensor, not sure if anyone has run one on here. Hopefully someone can chime in
 
Hmm. Ok.

If you go with DTC Assassin what does that process look like? As in, how often do you have to clear it, how long does it take, etc
 
Also…doesn’t clearing the code affect readiness/emissions testing results…?
 
Yes, and it needs to run a check of that system, which would either throw a code or pass for readiness. I forget how many readiness monitors need to be set for emissions but it’s not all of them. I got my STI through emissions for 3 years with a bad cat. It can be done it just involves some tricky planning
 
I have tried a couple different spacers and ideas so far and have had no luck. It's pretty impressive how fast it realizes the cats are not up to snuff. Usually throws a code within 15miles. Jb4 takes about a half second to clear the codes through the phone.
 
I have tried a couple different spacers and ideas so far and have had no luck. It's pretty impressive how fast it realizes the cats are not up to snuff. Usually throws a code within 15miles. Jb4 takes about a half second to clear the codes through the phone.

You used spacers with mini cats in them? The only 2 I've seen are from Fabspeed and M2.

As in, how often do you have to clear it, how long does it take, etc

You should PM shiftdown and ask him how often the CEL pops up with his mini cat spacers.
 
It’s a pain in the ass when the car gets old enough to require emission testing every year. I ran catless headers on my S4 for many years and although the car sounded great, every year I had to go through this ritual. My ECU was flashed to not throw codes, but failed readiness. For emissions I installed minicats, hooked my laptop up to my OBD port via a VAGCOM cable, cleared codes, then needed to drive around for about 20 miles and head into testing. It would only work from a cold start condition. There was a very narrow window and then readiness would fallback to failure. I would sit in the emissions testing line with my laptop hooked up checking readiness and at the last minute disconnect everything and stash it. It was somewhat nerve racking and after many years gave up and sold the car.

My point is every car is different and it took me many days and hours to stumble upon the method through trial and error.

The problem with changing out the OEM exhaust manifold or tubes in any way boils down to timing. There is timing between the upstream and downstream O2 sensors. Changing the path length of the exhaust flow confuses the sensors and throws codes.
 
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You used spacers with mini cats in them? The only 2 I've seen are from Fabspeed and M2.



You should PM shiftdown and ask him how often the CEL pops up with his mini cat spacers.
I have not. Just ordered a set. Probably won't be pulling the car out of storage till March or April so will be awhile to see if they work.
 
Has anyone tried o2 simulators? Back in 2002 I used these with catless headers in my civic (long time ago)... But these tapped into the o2 sensor lines, and skewed the secondary sensor to simulate scrubbing. Can we fool the cadillac ECU this way?
 
Has anyone tried o2 simulators? Back in 2002 I used these with catless headers in my civic (long time ago)... But these tapped into the o2 sensor lines, and skewed the secondary sensor to simulate scrubbing. Can we fool the cadillac ECU this way?
IDK if you can even find O2 sims anymore. The gov't cracked down on their availability years ago and fined the heck out of the sellers.
 
I would honestly buy the downpipes in a heartbeat if it weren’t for the CEL issue. Sucks.
 
So I installed the mini cat spacers today. Very tight fit but so far so good. 60 miles so far and no check engine light. Definitely the farthest it has been with no light since installing the downpipes. Will let you guys know some updates as they come.
 
So I installed the mini cat spacers today. Very tight fit but so far so good. 60 miles so far and no check engine light. Definitely the farthest it has been with no light since installing the downpipes. Will let you guys know some updates as they come.
This could be good!!! Keep us posted, thanks for guinea-piggin this.
 

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