John KM

I have a 2014 Sierra with the 5.3 liter engine. It has done 150,000 km (about 90K miles) without issue. 2 weeks ago while driving on the highway it started running rough and stalled. Towed it to a local dealer, the diagnosis is the engine is done. There's a rod knock in the bottom end and a broken valve spring. When this happened I was 8 days out of warranty. What I'd like to know is what is the cause of this failure? GM isn't any help, just ducking and weaving to avoid any responsibility. If there is a thread covering this issue and anyone can provide a link to it, or whatever other insights you may have, thanks in advance.