yukon is throwing 420 and 430 codes?

[rayninglead]

I've done some research and everything is pointing at the cats but the truck runs, starts, and drives fine mpgs are normal? Where should I look now?

 

[SunlitComet]

Get help on looking at the actual waveforms of the 4 sensors to find out if it is a legitimate "worn out cats" issue or if it is something else giving false data.

 

[rayninglead]

How do I check the 02 sensors?

 

[SunlitComet]

Get a shop with a good scanner that can read such data.

 

[rayninglead]

Ok so I fixed my exhaust and now I'm only getting the 420 code so which side is that? I'm going to switch 02s to see if it still throws code after I figure out what side is which. If memory serves me right that's the driver side correct?

 

[SunlitComet]

P0420 is the left bank. P0430 is the right bank. As measured using the rear sensors.

 

[2door2wheel]

i had the same deal on my truck. it ran great but it was my cats