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.