05 Sierra 5.3 cutting out

OLDARCTIC

MEMBER
2005 GMC C1500
103,000 MILES

I have an 05 gmc sierra with a 5.3. Last saturday on the highway it suddenly started running really rough and then died completely. I pulled over and looked underneath and the catalytic converter and even the muffler where the straps are were red hot. I let it cool for about 10 minutes and it started right up, I went for about a 1/2 hour with no trouble until I got almost home then same thing only no red hot exhaust, let it cool for 5 minutes and made it home ok. I've been driving it since with no problems at all, I have been trying to similate what I did saturday to try to make it do it again but it has been fine. The check engine light came on saturday and I got the codes monday but it went out monday and has been off since. The codes are p0336, crankshaft postition sensor and p0756, shift solanoid performance. I have since noticed a rattle in the right side catalytic converter, could this be the cause?

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

What I think has happened is the catalytic converter has melted down inside and come loose. When they plug, it will kill the engine if there isn't enough air flow. Also, they will get so hot that they will glow red hot. That is my first guess. Next, the crank sensor will also shut down spark to the engine. Thus, the engine will die. I would start with the converter since it is making noise and it was red hot. If it came apart inside, make sure it isn't partially plugging the muffler too. After that, drive it and see if the crank code comes up again.