My 2000 Chevy Impala LS 3.8 Ltr V-6 had a similar problem about three years ago.
Engine would die and within 5-15 minutes it could be started again.
No indication except the battery light in the message center and, of course, the engine had quit running.
No trouble codes on the computer.
Problem seemed to be random, but I found out later that it would happen within 30 minutes on the first trip of the day and it wouldn't happen again until left idle for a long period (overnight).
Anyway, The Crankshaft Position Sensor was causing the Ignition System to shut down, almost as if the ignition switch being turned off then back to on after the engine quit. The engine hasn't died again except when "I" shut off the ignition.
Thursday, September 3rd, 2009 AT 10:13 AM