I've got a 2005 Envoy, 4.2, 4X4. On a couple of occasions it died on the highway. It didn't sputter, but just quit. I got it home and ran the codes and found none. I replaced the crankshaft position sensor and now it will not start at all. Plenty of crank, but no start. I checked to see if it has a spark and it does not. I can hear the fuel pump running but haven't checked the pressure. It still isn't setting any codes. Any clue out there?