1999 chevy tahoe starter will only click when i start it?

[Doug F]

will the park/neutral switch have any thing to do with the truck not start in
the battery is good it reads 12.8 v when engine off with no key in i can go from p to d

[MISTER TWO]

Charge your battery.

Batteries should read 12v when the engine is off, or 14v when the engine is running.

Your battery is dead, so you need to jump the car or purchase a new battery.

Why is it dead? GOOD QUESTION! The battery may be done, or the alternator may be dead and not charging it. Ensure the car really does put out 14v when the engine is running.