Where is the neutral safety switch to 1999 Mazda B4000 automatic pickup truck?

The neutral safety switch on a 1999 Mazda B4000 automatic is located on the transmission itself. It's not easily accessible without some mechanical knowledge and usually requires going underneath the vehicle. It's a part of the transmission's linkage assembly.

You won't find a readily visible switch like on some cars. To pinpoint its exact location on your specific transmission, you'll likely need a repair manual specific to your 1999 Mazda B4000 automatic transmission. A shop manual will have diagrams and instructions for accessing and replacing it.