'16 Prerunner Rear Differential Lock help needed

I'd imagine you would have to put the transmission in s mode and limit it to 1st gear

 

Nothing grinds my gears more than people trying to engage their locker on flat ground and saying it won’t engage. People, stop pressing buttons unless you need it. The rear locker engages easily when you are in low traction situations.

 

Absolutely...where did OP say he did this?

 

Maybe because they'd like to know it's working and how to use it before needing it? This is a perfect example of figuring out something beforehand. If OP waited until he was out stuck on the trail he'd be SOL.

Also these lockers do not easily engage. I don't have one, but my buddy does. Seems like half the time it gives him a little issue engaging.