"MIL" (ck eng) light is on for a PO420 DTC? Do I need a new cat? I would appriciate anybody who could help. thanks

 

P0420 is catalytic converter efficiency below minimum specs.

Probably time for a new cat, but have you changed anything else? it could also be a dirty O2 sensor. you can clean them with electric parts cleaner. you can also use carb/choke cleaner if you're careful

 

You could also fill in the specs about your truck when you register! And it's probably time for a new lower intake gasket.

 

Just remember if you do in fact need a new cat check out summitracing. I picked up a
hi flow stainless steel magnaflow cat for under $100.

 

420 Hmmmmmmmmmm ?? - Not enought THC in your system

 

I'll try cleaning the sensor, how do I know if it's the sensor or the cat? Or the intake gasket? I haven't done anything yet, just some banging on the muffler and it's loose inside. The cat might be too haven't hammered on that yet.
(I try to get more THC in, maybe I'll forget about that durned light! )