P0420 CEL Code after installing Borla X Pipe
Thread Starter
Burning Brakes
Joined: Aug 2011
Posts: 764
Likes: 258
From: League City Texas
P0420 CEL Code after installing Borla X Pipe
Installed a Borla X Pipe and now I have a check engine light. I used the Torque app on my phone and the code is P0420 "Catalyst System Efficiency Below Threshold (Bank 1).
I just jacked my car up and my first thought is that the X Pipe isn't bolted tight enough to the primary cat and thus an exhaust leak but visually it looks fine. Anyone have any ideas? I suppose a cat or 02 sensor could have gone bad but it seems like weird timing that the CEL would come on shortly after installing the X Pipe, also the car only has ~5,500 miles on it, granted they're pretty hard miles.
I just jacked my car up and my first thought is that the X Pipe isn't bolted tight enough to the primary cat and thus an exhaust leak but visually it looks fine. Anyone have any ideas? I suppose a cat or 02 sensor could have gone bad but it seems like weird timing that the CEL would come on shortly after installing the X Pipe, also the car only has ~5,500 miles on it, granted they're pretty hard miles.
Supporting Vendor
Joined: Feb 2015
Posts: 35,686
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Installed a Borla X Pipe and now I have a check engine light. I used the Torque app on my phone and the code is P0420 "Catalyst System Efficiency Below Threshold (Bank 1).
I just jacked my car up and my first thought is that the X Pipe isn't bolted tight enough to the primary cat and thus an exhaust leak but visually it looks fine. Anyone have any ideas? I suppose a cat or 02 sensor could have gone bad but it seems like weird timing that the CEL would come on shortly after installing the X Pipe, also the car only has ~5,500 miles on it, granted they're pretty hard miles.
I just jacked my car up and my first thought is that the X Pipe isn't bolted tight enough to the primary cat and thus an exhaust leak but visually it looks fine. Anyone have any ideas? I suppose a cat or 02 sensor could have gone bad but it seems like weird timing that the CEL would come on shortly after installing the X Pipe, also the car only has ~5,500 miles on it, granted they're pretty hard miles.
thats very rare to happen on just fitting a x pipe sir, check for leaks and that the down stream 02 sensors are conencted correctly, if you end up needing a tune let me know and i can hook you up sir
Burning Brakes
Joined: Nov 2001
Posts: 973
Likes: 221
From: Lake Norman NC
Installed Corsa X-pipe on my 2015 C7 and before trade in removed the x=pipe and installed on my 2016 ZO6. No code at all even after 15000 miles on my C7. It must be the exhaust leak, tighten clamp check all wiring clear cel and you should be on your way.
Thread Starter
Burning Brakes
Joined: Aug 2011
Posts: 764
Likes: 258
From: League City Texas
I've checked the connections and they are tight. The X Pipe bolts to the primary cats (as opposed to clamped) and those are tight. I monitored the rear o2 sensors and Bank 1 (the side that tripped the CEL) doesn't seem to be reaching like Bank 2. Possible that the o2 sensor went bad but weird timing. I'd swap Bank 1 and Bank 2 sensors to see if the CEL changes Banks, but the o2 sensors look pretty hard to get to.
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Burning Brakes
Joined: Apr 2016
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i don't care what anyone else says, exhaust donuts are one time use. 420 codes are usually a cat, o2 sensor or exhaust leak, you can have someone cover your tail pipes and see if it's leaking where the Xpipe mounts to the cats. Most likely this is where your problem is.
Melting Slicks
Joined: Nov 2012
Posts: 3,163
Likes: 686
From: SUFFIELD CONNECTICUT
The exhaust donuts are not one time use. I have done my C7 and did a off, on, off, on with my C6 Z06 and reused the exhaust donuts with no problems. Many x-pipe swaps have been done on this forum with no issues with reusing the exhaust donuts.
Melting Slicks
Joined: Nov 2012
Posts: 3,163
Likes: 686
From: SUFFIELD CONNECTICUT
i don't care what anyone else says, exhaust donuts are one time use. 420 codes are usually a cat, o2 sensor or exhaust leak, you can have someone cover your tail pipes and see if it's leaking where the Xpipe mounts to the cats. Most likely this is where your problem is.
Burning Brakes
Joined: Apr 2016
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Melting Slicks
Joined: Nov 2012
Posts: 3,163
Likes: 686
From: SUFFIELD CONNECTICUT
Moderator emeritus
Joined: Jun 2001
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From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
Oh God! We have a "bonding" moment! 
Honestly, the donuts can be a bit of a prig at times if they turn slightly during the reuse. I know it is a PITA but I'd loosen all the connections on the exhaust and then tighten the x-pipe at the CATs evenly on the bolts and give it another whirl.
Elmer
Honestly, the donuts can be a bit of a prig at times if they turn slightly during the reuse. I know it is a PITA but I'd loosen all the connections on the exhaust and then tighten the x-pipe at the CATs evenly on the bolts and give it another whirl.
Elmer
Thread Starter
Burning Brakes
Joined: Aug 2011
Posts: 764
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From: League City Texas
I'm going to try and buy new gaskets / donuts today (if they're in stock). However the rear o2 sensors are maybe 8-12 inches upstream from this connection. So if it was leaking why would it matter since it is already past the sensors?
Moderator emeritus
Joined: Jun 2001
Posts: 18,599
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From: Jacksonville Florida BWO Dayton, Cincinnati, Bloomsbury NJ, Cincinnati
2015 C7 of the Year Finalist
Elmer
Thread Starter
Burning Brakes
Joined: Aug 2011
Posts: 764
Likes: 258
From: League City Texas
http://www.jegs.com/InstallationInst.../157-60548.pdf