GM Service Manual Online
For 1990-2009 cars only

All of the automatic transmission equipped models of this vehicle are equipped with steering columns that contain a mechanical neutral start system. This system relies on a mechanical block in order to prevent starting the engine with the transmission in any position other than P (park) or N (neutral).

A park lock (backdrive) cable connects the ignition switch to the gearshift selector. This cable prevents the gearshift selector from moving unless the ignition is in the ON position. Refer to Automatic Transmission for further information.