LemonySoda60432
Newbie
Good afternoon. I have a 1999 GMC C1500 with a 350 Vortec. Bone stock unless the previous owners messed with her. I have slowly been restoring the truck and it is my daily. My first car too, as a matter of fact. I have one problem though. When I bought her she had no check engine light, after a few months she flung a downstream o2 sensor code if memory serves. I replaced that sensor with a GM genuine part and reset the light. After driving for a while, she popped a light again so I pulled into autozone to get it scanned. Now I am getting both P0430 & P0420! With their little printout saying the most likely culprit(s) are the Fuel injectors and/or the intake manifold gasket. Problem is I don't think it could be the manifold gasket because she doesn't idle high. Any ideas on what it could be? Thanks.