Fault: A GM Chevrolet Limousine engine has serious vibration after accelerating and rapidly decelerating with the engine running and transmission in neutral. About half a minute, the vibration disappeared. Diagnosis: I applied GM Tech 2 diagnostic scanner, an authentic GM software in the Tech2 Flash, supporting for on-board diagnostics on all GM systems 1992 thru current year. What’s more, with TIS2000 software, it can program GM cars before 2007. …