A couple of days ago my service engine soon light randomly came on. Pulled the code with my scan gauge and it was P0420. I called my buddy thats a tech at the dealer and he just said that it was to do with the cats not working right. I cleared the code and yesterday when I went to town again it came back on, same code. I have the dynatech headers and cats. I was wondering if anybody else has had this code with the dynatech cats? I think they only have 7-8k on them. I wouldn't think one would be bad already. But if thats the case im just gonna take them off and gut them or just do away with them completly and have Allen delete the rear 02 sensors. If anybody has any suggestions or comments you have the floor.

 

Code P0420: Catalyst System Efficiency Below Threshold (Bank 1)

Could very well be a bad cat, or a rear O2 sensor giving an incorrect reading...90% of the time when I've seen that code it's been the cat though. If you have any logging software, you need to look at what the rear Bank1 O2sensor is doing....if it's switching from rich to lean very quickly, like the front O2, then the cat is at fault.

 

I will see If i can run a log and post the results, I dunno if the aeroforce scan gauge can log or not. I hope its not a bad cat, but if it is oh well.

 

The GM flow chart for that code is 2 steps.
1. inspect cat for damage
2. If damaged or not replace cat....

 

Yeh, I don't have gm cats though.

 

When I had this code on my yukon the cats were shot and the "honey comb" material had broken up and was clogging my exhaust...pieces were sitting against the o2 sensors bc they were too big to pass. Granted these were old stock cats but you never know....

 

I hope thats not the case, but like you said you never know.

 

I would just pull them loose and clean them up. and have allen turn off the rear o2s