ahhhh welcome to the V6 Blowup Club!!! Went through the same thing 6months ago. Good luck getting GM to do anything about this, they try to wipe their hads clean of it even if you're in warranty. I still cant believe chevy hasnt released a recall for these LLT motors. With how many have this issue its gotta be an under-engineered part or oil circulation issue.

What year and how many miles? How long have you owned it? Are you the original owner? The inside of that engine does show signs of milage and possible some extended oil cycles regardless of the monitor.. Still that is not the cause and it could have been some other have mentioned related to those cylinders either with oiling, bearing, or running condition causing excessive load to break down the oil there and extra pressure on bearings.. Any pinging or noise before it quit and for how long? What fuel do you normally run?