So, I've got a 96 Cherokee. The other day after driving for several hours, it threw a CEL (P0420, Cat system efficiency below threshold bank 1). I cleared the code and it hasn't come back on. But, I have been feeling a slight loss in power. Its not huge, and there's a possibility its in my head, but its much quicker to downshift on the interstate and what not. I'm wondering if the Cat is clogged, and what would happen if i just emptied the cat. Have done this on previous (non OBDII) vehicles with success. Will it throw a CEL? Are there any other options? Thanks

 

You can delete the cat, it may throw a check engine light but it won't affect performance, because the o2 sensor that the computer uses to measure your air/fuel ratio is before the cat. My 97 doesn't have a cat and I don't get a CEL because of that.

 

Just be careful if your state requires inspections. Technically it's illegal to remove a cat from an on-road vehicle that originally had one. If you don't have emissions testing, hollowing it out is technically illegal, but in theory without emissions testings, you'd still pass the visual cat inspection. I, of course, would never suggest any illegal activity, but here in MA I'd think some rogue individual could easily go the hollow-out method and still get a sticker.

 

Yeah, I'm in SC. Been running cat-less vehicles for years. You can get away with pretty much any kind of exhaust here. And no emissions testing.

 

I believe we are free to talk about CAT stuff now let me know otherwise. With that said I run a 96 with a hollow cat. I opened it like a clam shell and took the bricks out whole then weld back shut. Welds are on top and hidden. It did throw a cat code which was resolved with a defouler. CT requires visual cat and obd2 plug in emissions with no more than 2 non ready I/m monitors, including cat nonready, for the 96 to 99 or 01? I can't remember at the moment.

 

Did you notice any changes in performance or gas mileage?

 

No performance issues with a cat code. I had major issues when the catalyst bricks turned sideways and restricted the exhaust hence why they got removed.