While driving, the vehicle shut off without warning. It was in-traffic when this occurred and subsequently blocked traffic. I tried to restart the vehicle many times. It would start and then die within a few seconds. Since the vehicle would not remain running, it was impossible to shift out of the ‘park’ position. Since it was in ‘park’, the vehicle could not be readily moved out of traffic. This failure is a safety hazard! The vehicle was towed from the scene. The dealer diagnosed the problem as the ‘Powertrain control module lost communication the the fuel pump driver module causing no fueling to engine from low pressure fuel pump U18A…’ The fuel pump control module had internal communication circuit failure. GMC module 13554820 was replaced.