i have a 99 sable with only 66,000 miles on it. When i was driving it, it completely shut off on its own and wouldn't start back up. The mechanic told me i needed a new fuel pump in which he replaced. the car started up and drove for about two blocks when it shut down again. He than told me i needed a new Cpu. Everything still works within the car (lights, radio, etc) but wont make any type of sound when i try to start it. Could this be a Cpu problem? if so how come the mechanics diagnostics said the fuel pump was the problem and why did the car drive again after installing the new fuel pump.