mckpaul
TYF Newbie
Well, to follow up on the P0430 code on the new cats, it's resolved. Don't have a definitive conclusion as to the exact cause of the light, but here's how it went down.
I was thinking of pulling the y-pipe down and pulling the exhaust manifold off to put a new gasket and properly torque it, if nothing else, to know there was no leak. As I looked over the engine, I noticed the far back manifold mounting bolt on the passenger side appeared to be missing, but could feel the broken off stud in the hole. Looking at the driver side, it was the same way. Since a shop had just had the heads off a week or two before, I took it back and requested all of the exhaust manifold bolts be present, even purchased a new set of Dorman exhaust manifold bolts and provided them to the shop to use. They were able to get the passenger side out, but the driver side required pulling the head again to get the broken bolt out. So I got the truck back hoping all would be OK, but the P0430 came back about 3 days later.
So looking at the exhaust manifolds again, I noticed the far back bolt on the passenger side was not one of the new bolts I provided (it was old and a different color), and didn't look like the bolt head was seated completely down on the manifold. I also suspected they probably just reused the manifold gaskets since they had just put them in a couple of weeks before. At this point I'm tired of dealing with someone else's work, and didn't want the same guy working on the truck that already got flagged for breaking exhaust bolts off on reassembly and just leaving them, so I bought new manifold and y-pipe gaskets, and tore into it myself. That last bolt that he substituted at the back of the manifold was not the correct thread, I think it was SAE instead of metric, but close. Luckily it was short. The thread damage on the head was only about 5 threads deep. But using that bolt, while torqueing the manifold bolts, since it was forced in it was really tight and not giving an accurate torque reading. So he had no way of knowing if it was tight enough to make a seal, and my guess is he just stopped in fear of it breaking off. I was able to back it out and clean up the hole with a M8-1.25 tap, and the replacement bolt is 30mm long (about 1-1/8") long enough to get a good bit into the deep undamaged threads. So I did get the new gasket in with all 6 bolts properly torqued.
Anyway, not being sure of the heath of the new cats/y-pipe, I also purchased a used y-pipe off a rear-wrecked '12 Sierra, so instead of taking a chance with the new cats and having to do the work again if it still reported in as bad, I just installed the used set instead of the new ones. So I'm 100% sure there are no exhaust leaks and I have used known good OEM cats in place, and all the monitors (except EVAP) have now set, including the cat monitor. The O2 sensor graphs on the scan tool look good so the problem is solved. I could have been an exhaust leak at the manifold, it could have been just the truck not liking the aftermarket cats, it could have been just a bad new cat on one side, I will never know, but I do for certain that the problem is gone, and that damn light is off. I just wanted to post that it was resolved since I started the discussion, and say thanks for all the suggestions and input!
I was thinking of pulling the y-pipe down and pulling the exhaust manifold off to put a new gasket and properly torque it, if nothing else, to know there was no leak. As I looked over the engine, I noticed the far back manifold mounting bolt on the passenger side appeared to be missing, but could feel the broken off stud in the hole. Looking at the driver side, it was the same way. Since a shop had just had the heads off a week or two before, I took it back and requested all of the exhaust manifold bolts be present, even purchased a new set of Dorman exhaust manifold bolts and provided them to the shop to use. They were able to get the passenger side out, but the driver side required pulling the head again to get the broken bolt out. So I got the truck back hoping all would be OK, but the P0430 came back about 3 days later.
So looking at the exhaust manifolds again, I noticed the far back bolt on the passenger side was not one of the new bolts I provided (it was old and a different color), and didn't look like the bolt head was seated completely down on the manifold. I also suspected they probably just reused the manifold gaskets since they had just put them in a couple of weeks before. At this point I'm tired of dealing with someone else's work, and didn't want the same guy working on the truck that already got flagged for breaking exhaust bolts off on reassembly and just leaving them, so I bought new manifold and y-pipe gaskets, and tore into it myself. That last bolt that he substituted at the back of the manifold was not the correct thread, I think it was SAE instead of metric, but close. Luckily it was short. The thread damage on the head was only about 5 threads deep. But using that bolt, while torqueing the manifold bolts, since it was forced in it was really tight and not giving an accurate torque reading. So he had no way of knowing if it was tight enough to make a seal, and my guess is he just stopped in fear of it breaking off. I was able to back it out and clean up the hole with a M8-1.25 tap, and the replacement bolt is 30mm long (about 1-1/8") long enough to get a good bit into the deep undamaged threads. So I did get the new gasket in with all 6 bolts properly torqued.
Anyway, not being sure of the heath of the new cats/y-pipe, I also purchased a used y-pipe off a rear-wrecked '12 Sierra, so instead of taking a chance with the new cats and having to do the work again if it still reported in as bad, I just installed the used set instead of the new ones. So I'm 100% sure there are no exhaust leaks and I have used known good OEM cats in place, and all the monitors (except EVAP) have now set, including the cat monitor. The O2 sensor graphs on the scan tool look good so the problem is solved. I could have been an exhaust leak at the manifold, it could have been just the truck not liking the aftermarket cats, it could have been just a bad new cat on one side, I will never know, but I do for certain that the problem is gone, and that damn light is off. I just wanted to post that it was resolved since I started the discussion, and say thanks for all the suggestions and input!
