Check engine light (P0420) after catted downpipe & CEL defouler install

[Drew J]

I installed the catted downpipe from Whoosh, and it caused a check engine light for p0420, which is catalytic efficiency. I then bought the CEL defouler from Whoosh, and had it installed last week. The CEL didn't come back on after it was cleared during the defouler installation, but then it came back on over the weekend.

Any idea what might be going on? Did they not install it correctly? They didn't use all the parts that came with the defouler, there are two small open ended cylinders/sleeves/spacers left over.

Thanks in advance.

 

[SteveS]

https://www.fixdapp.com/blog/p0420-code

Exhaust leaks, bad catalyst, bad O2 sensor, misfire, bad air/fuel ratio

 

[slopoke]

Since you referenced that you have 2 small cylinders left over, I'm assuming that you got the Vibrant J shaped defouler. The cylinders come with three orifice sizes, which size did you install? I just installed a pair into my current vehicle and started out with the middle size orifice. No CEl lights in over 400 miles. Check which orifice you've got installed and go up or down in size to get your CEL to stay off. Good luck.

 

[jessemon1106]

If you didn't use the small insert in the o2 spacer I'd switch it over. I just went from stock dp to catless without issues.

 

[Ranbo]

Looking into a maperformce cat back for my Fiesta 2017st would like to know if it would set the check engine light on staying with the stock down pipe anybody can help me out thanks

 

[arlisscm]

Looking into a maperformce cat back for my Fiesta 2017st would like to know if it would set the check engine light on staying with the stock down pipe anybody can help me out thanks

Cat-back won't impact anything. Both o2 sensors are on the downpipe, so if that's left stock, no issues.

 

[Sam4]

Looking into a maperformce cat back for my Fiesta 2017st would like to know if it would set the check engine light on staying with the stock down pipe anybody can help me out thanks

MAPerformance and Woosh catted, 1 year later. Needed the defouler and used the smallest insert - 10 minute job, the hardest part is crawling underneath. There would be no reason an exhaust replacement would set it off - it's about the cat (or lack there of) and o2 sensors.

 

[Ranbo]

Would a spectrum cold air intake put the check engine light on or mess any codes up thanks

 

[TyphoonFiST]

Would a spectrum cold air intake put the check engine light on or mess any codes up thanks

No as long as you use the correct adapters if its 2016+ if its 2015 and below you wont need the evap emission harness junk. Buy a good intake setup from either Whoosh or 2nd hand off the Forum or Facebook mkt place. Check the Forum here in the forsale section too