Power Steering Pump problems of the 2012 GMC Sierra

After exiting interstate lost steering and brakes briefly in parking lot. Pumped brake and both returned after a hissing sound. Recurred a few times in next 6 months or so. Then, in the fall of 2013, lost steering and brakes on I-49/us71b heading south from joplin, missouri. You could pump the brakes and briefly regain, but for the most part all steering and brakes were out. Took truck to GMC dealer where purchased new in bentonville. Dealer confirmed no steering and brakes and damaged bumper while vehicle in its possession by bumping into parking lot barrier. Dealer diagnosed power steering pump problem and indicated that brakes and power steering are tied to same pump/system. Dealer replaced pump but said that even though it was a two or three part system could only replace the pump. Truck continued to have problems and was taken back to dealer following similar episode where lost both steering and brakes. Dealer refused to do anything to replace the other components because could not replicate the problem. Dealer claimed no notice of any other complaints of this nature form gm or any other source. We pleaded with the dealer about it being a safety issue and asked that the dealer replace the other components it identified as possibly related. Dealer took no further action claiming without gm telling them to look further and pay for it they could do nothing else. Truck continues to have problems intermittently. It is nonsensical for a truck to have two significant safety systems tied together with no secondary support or fail safe system to guarantee that operator still have brakes and steering at all times. Truck also has rattles consistent with the service letters / issues noted on this website.