p0420 toy. trunda 03 v8 new o2sensors no#1& 2 replaced, can,t get check light off. thanks

Question

03 trunda v8 runs great just like new,changed ( 2 )02sensors ,bank1 new gas cap ckecked gas filter carcold filter.check lite stil on,i drove114mi after reset before lite came back. (p0420)

Answer 1

P0420 usually 90% of the time means the catalytic converter is bad, if there are no exhaust leaks

P0420 is bank 1 (driver side)

In some cases these might work if the catalytic converter  is not already overheated or damaged. Use 91 octane from Shell along with a good fuel system cleaner like 3M or BG 44k and maybe do any intake flush to decarb the engine.