Look on the left rear corner of the transmission to see if there's a three-wire connector. If there is, that is the neutral safety switch and backup light switch. By 2006 they changed the circuit to a stupidly complicated computer switching circuit. I don't know which year that started.

If you have that plug, turn on the ignition switch, disconnect that plug, and use a stretched-out cotter pin or paper clip, or even a needle nose pliers to connect the two outer terminals in the plug. If you look closely when you do that and you see a tiny spark, that means current is flowing and the backup lights are on. If you can't see that spark, you or a helper will have to look if the lights turned on. If they do, that proves the entire rest of the circuit is okay and you need to replace the switch.

Answered by caradiodoc (expert)
17,655 answers provided