For the past several months, when I release my emergency brake, the handle would not go all the way down and stay there. It would come up a notch. the other day I crawled under the truck and found that the arm that the single cable goes to to actuate the rear cables was covered with dirt and dry. I sprayed some PB blaster on it and some white lithium grease on it and worked it vigirously.
Since this, my emergency brake works like a charm!
I thought I would post this solution so maybe it could help someone.

 

The light also comes on when you're low on Brake Fluid

 

Super common for the pickup cables to get all corroded up in the back end. The 4runner has sealed cables. The pickup uses rubber boots that just disintegrate after a few years.

Mine only worked after both sections snapped and were replaced.

 

solution: open the dash and break the bulb. J/K