Engine Code P0420

I had my CAT converters stolen, and then got after market replacements. The truck runs great but after two days the check engine light came on and threw this code (P0420). The truck is still running great, but why is it throwing this code and how do I fix it?

 

My experience with aftermarket cats hasn't been all that good, as some will throw the cel, or it could be a faulty o2 sensor now.

 

Fkin Cat Thieves should be castrated then hung from from the nearest tree whilst
being beat with a baseball bat and left there to rot. Hang a big sign from their feet
labeled CAT THIEF - see how they like it now.

 

Check your 02 sensors.

 

If they didn't install them correctly and there's a leak, the O2 sensors will read the cats as being bad and trigger that code. Either that or the aftermarket cats they installed were poor quality and not satisfying the parameters of the O2 sensors. The cheap ones have way less of the (expensive) material in them that filters the exhaust gases.

OEM cats are crazy expensive not just because Toyota sells them. Magnaflow or Walker are the only aftermarket brands I'd trust personally.

 

I had a crack in the weld on the flange of my drivers side cat and it threw this code. It could be anything up or downstream from the cats from a loose seal, to a crack, to a dirty or faulty or misinstalled O2 sensor.

Take it back to whoever did the replacement work and have them check it. If it a leak it’s usually pretty easy to find.

 

You can go to brasil and your wish can come true , nowadays people just get cancelled for saying the wrong things lol