[richard2717]

My work truck is a 2008 GMC Sierra 2wd with 4.3 and automatic. Has 295K miles and have had no issues with truck other than normal maintenance stuff until about a month ago. Truck started running rough so I pulled it in the shop and found #1 plug wire burnt in half. Replaced that wire and plug (even though old plug looked as good as the new one) and everything back to normal. Fast forward to last Wed., Truck barely idles then jumps to high rpms then cuts off. While revving up the lights also start flashing (all the lights, dash, headlights and parking) bright to dim the whole time. Since we were near the dealer I bought the truck from I dropped it off to them. They called Friday morning and said Cats were clogged up and there was nothing they could do with that issue. They also said truck would not run long enough to tell anything on the computer. So, I paid them $90 then a rollback $60 and brought truck home.
I had a complete motor/ drivetrain takeout sitting here from a wrecked 07' that i bought. That truck only had 29K miles on it when wrecked, so I feel pretty good about the cats being good. I put truck up on my lift and removed the Y pipe with the cats and replaced it with the one off of the 07'. Had to pie cut my existing tailpipe and reweld to get the tailpipe to the correct angle, but everything came together nice. It went together well enough I knew the problem was not fixed lol. Sure enough dropped truck back down and no change in startup.

I bought a cheap $20 code reader and it is throwing several codes.

P0301 which is still a misfire on cyl 1 if I read correctly

P0420 which if I read correct is still an issue with the cats

P0442 small leak in evap system

The other 7 faults were coming up as all 00000

It also had 2 C codes

C0300 which comes up as 4wd not working (which is correct since truck is 2wd)

C0700 which I could not find a definition for

With all that said
Truck has 295K so I don't see a need to dump tons of money since it is a work truck.
I don't know much about all of the emissions/ electronics on the newer stuff
Since it runs no better I see no need to take back to dealer.

Can someone point me in the right direction? the lights flashing is what has me concerned the most. It makes me think there may be a bigger problem.

Thanks
Richard

BTW the 07' was the classic body style and I have found that most everything on it is different from the 08' so I am not sure short of swapping in the complete engine how much good it would do.

Sorry for the long write up