Code P0420 Catalyst System Efficiency Below Threshold (Bank 1)
 

Hey guys, I need to replace a faulty catalytic converter, I guess the JDL UEL header didn’t work out in the long run. Is there any advice on replacing this? I’m not sure if I have to spend a whole $1300 on a part or looking for a simple basic one that could be cheaper. Thank you

You need to elaborate more on what mods you have. So you have a JDL catted UEL header, you do know those are not guaranteed to not give you a P0420 right? Doesn't mean the cat has failed. You can either try using one of those cheesy O2 spacers or get the the car tuned proper and have P0420 disabled.

Verify the problem, then repair. A code is a result of a symptom, but you haven't diagnosed the actual cause.

Simple fix. Get an OFT and run a tune to take advantage of the header plus it will disable the code. As others have said just because you have a cat, if it's not stock no guarantee you will not get a code. How long have you had the header? I know JDL had some quality issues with there old cat supplier and that's why they stop selling them for a while.

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