ok, i'm kind of at the edge of my ability to investigate this problem.

the car is a 2001 chevrolet impala 3.4l. occasionally, it will not start in park. as it is my mother's car, i gave her a notecard with very explicit instructions about how to start the vehicle in neutral, which, up to very recently, has "fixed" the problem. the last time this occured, however, shifting to neutral did not work. it did start after multiple attempts to start it in neutral, though. i assumed that the problem lay in some manner of neutral safety switch, so I went down to the parts store and procured the aforementioned switch for the vehicle, as well as a copy of how to change the switch from the service manual in the public library. well....get down to business--the car does not have any manner of neutral safety switch on the transaxle. an opened service manual for the impala at the parts store revealed that the two holes in the transmission were for some manner of safety switch, but none was there (or was ever there). the manual says that 2003 on impalas have this function integrated into the security system, but, of course, this is a 2001. is there any chance that maybe the brake switch has something to do with this issue? i'm somewhat certain that this may have made a difference, what with her likely leaving her foot on the brake in some instances (and in others, not). there is an issue with gm cars not cranking because of the lock tumblers and the security system, but an obdII scan did not show the applicable code. any gm people out therer? thanks in advance.