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Discussion Starter · #1 ·
Hi so I bought a 2013 focus st. I loved it until,i received,p0420 code. All,i can see on car is that it has a borla exhaust and trying to figure if i have a catless dp or not. Code would suggest i have no cat but here are some pics for you guys as you guys would know best. Sorry for the pics. It was,the best i could do.
 

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Seems to be a catless downpipe with a cat placed downstream...You are getting codes becuase you should have 2 sensors, one upstream of the cat and one downstream of the cat. But because of the way it is setup they are both upstream causing the rear O2 sensor to think the cat is no longer working.

To solve this would mean getting a different downpipe that is either catted and cut that other one out. Or run a defouler on the rear O2 sensor to trick the sensor into believing the cat is still upstream of it.

I have a stock downpipe laying around if you would like to buy it, otherwise just buy an aftermarket catted one and follow the above statement.
 

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I dont remember the cat being there LOL. Great example of why I would never ever ever buy a used performance based car.
 

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Even a Honda? Dont mind the cat, it just eats carbon.
Whoever did this was a hack, instead of putting the cat where it should be (by buying a catted downpipe) the previous owner chose to do something janky and install a cat on this car improperly. I agree with sometimes used performance cars are a bad idea, as the previous owner is not guaranteed to be intelligent enough to work on cars or discern who is intelligent to work on cars for them...
 
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His P0420 is only for emissions. Its not a real threat to the car. I may preform differently but nothing too bad. HOWEVER, i'd also would want this taken care of.
 

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His P0420 is only for emissions. Its not a real threat to the car. I may preform differently but nothing too bad. HOWEVER, i'd also would want this taken care of.
I know it isn't a threat, but in emissions areas it just sucks to have to deal with this kinda work. Hell I am catless and registered in an emissions county, so a defouler and praying are needed. ;P
 
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81MzxpbclUL._SX355_.jpg


Are we 100% sure that is a cat after the muffler? Looks an aweful lot like a resonator, similar to the one in the picture.

If you are running a catless DP, it is more than likely that the previous owner had a tune on the car. If you did not receive the tuner with the car, I would suggest starting there.

When I went with a catless DP, I used a defouler and I have not gotten any codes.
 
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View attachment 244434


Are we 100% sure that is a cat after the muffler? Looks an aweful lot like a resonator, similar to the one in the picture.

If you are running a catless DP, it is more than likely that the previous owner had a tune on the car. If you did not receive the tuner with the car, I would suggest starting there.

When I went with a catless DP, I used a defouler and I have not gotten any codes.
I went cat-less with EFR's platform set up, never need a defouler. Tune usually takes care of this.
 

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View attachment 244434


Are we 100% sure that is a cat after the muffler? Looks an aweful lot like a resonator, similar to the one in the picture.

If you are running a catless DP, it is more than likely that the previous owner had a tune on the car. If you did not receive the tuner with the car, I would suggest starting there.

When I went with a catless DP, I used a defouler and I have not gotten any codes.
I am 95% sure that is a cat, most race cats have a shell that is formed without welding whereas most resonators are welded together. This cat looks like this cheap race cat and even the forming marks on the outside match. s-l225.jpg it would be easy to check but I don't see why someone would put a resonator that close to another.
 

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I am 95% sure that is a cat, most race cats have a shell that is formed without welding whereas most resonators are welded together. This cat looks like this cheap race cat and even the forming marks on the outside match. View attachment 244474 it would be easy to check but I don't see why someone would put a resonator that close to another.
Dang this seems like a high possibility, only way to really find out is take a grinder to it and take off the welds' and look inside.
 

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Pardon if I'm missing something, but why is this so janky? The welds look like upper end exhaust shop welds to me. Maybe not the beauty of tig, but they ain't bad.

Why not just tell the guy to get a bung welded in post cat, get a wiring extender, and run the second 02 after the race cat, plug the second bung upstream. Voila, no more code, AND technically, he'll still pass emissions.

Having the cat as far away from the head as possible will limit the performance of the cat as an emissions device, but will increase the breathing area of the turbo's exhaust. Win/win, I say. This probably flows better than a purchased catted downpipe as well.
 

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Discussion Starter · #16 ·
Thanks for all the replies just got my new AP from a good guy on ebay has panda tunes saved on it. My suggestion is most likely cheap cat after looking under the car all day. Got this from the ford dealer looks like they were just trying to make it pass inspection. Will be going to a shop to get that ugly looking cat off and running existing catless dp and borla hopefully with tune i should be a step closer to getting this light going away!
 
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