All GM fuel injected vehicles that I'm aware of use an oil pressure switch to power the fuel pump. There is a 2-second "priming run" to pressurize the fuel rail anytime the ignition is turned on, and/or the pump runs continuously while the starter is engaged, then the switch takes over to keep the engine running. It used to be called a "rollover switch" to be sure the engine would stop in case of a rollover accident. Ford used something similar, an "impact switch" that would trip in a wreck with more deceleration than a fender-bender. The idea is to make sure the fuel stops flowing anytime there's the possibility of broken fuel lines or any possibility of gasoline spillage.
Jerry
