The root cause turns out to be a mechanical design problem.

GM issued a TSB number 15-NA-051 dated Nov 5, 2015. This TSB claims that the bracket that holds the back seat bottom cushion in on the driver's side can interfere with the fuse box cover and put pressure on the fuel pump relay. Sure enough, my fuse block cover has shinny rub marks that line up with the bracket. In time the wiring under the fuse block can become corrupted and short the relay to ground, causing too

much current which causes the relay and the fuse block to melt. Once this condition exists, a new relay will also melt.

Their solution is to cut 5 mm off of the end of the seat bracket and install a low profile relay and a new fuse block. GM recommends relay part number 88953222. I think the wiring also needs to be repaired although the TSB doesn't say so.

It looks like a poor design causes a seven hundred dollar (non)repair.

car shut off while driving at hwy speed. steering? brakes?

My brother was driving my Moms car and it quit running while driving at highway speed. Checked relay and it was bad so we replaced that at about40 bucks. Car started and ran 5 miles and died again. Replaced fuel pump at about 300 bucks and it did the same thing. Found the fuse block where the pins are was melted because we noticed the underside of the back seat was discolored like it had been about hot enough to catch fire! Started investigating and found several (Not like 10 or twenty but closer to 50 or more complaints about this and some had caught fire!!! No recalls! seriously?? I bet the CEO of GM would have a recall tomorrow if he had to transport their grandchildren in a potential bomb!!! My Mother is 70 years old and still very active and of course on a fixed income and I recommended to that she buy a reliable GM car which she bought new and now she is deathly afraid to even drive the car by herself even after she had the entire fusebox replaced at a GM dealership for an additional $776.52. I have and my mother has been dedicated GM owners since I was a child and I'm 46 now. Step up and claim your problem before somebody dies from this issue that you are very aware of!!!!!!