My TV is a 2008 Tacoma 4dr 4X4, 4.0L V-6, auto. I tow a 2001 Casita
17 Spirit Deluxe, an '84 Scamp
13, & a 10' 2006 homebuilt teardrop trailer. The Casita
& the Scamp
are both equipped with electric brakes
. After extensive shopping I bought & installed a Tekonsha Prodigy P3 controller. Also ordered the 'plug'n play' pigtail for my Tacoma from Takonsha. The wiring harness & plug/receptacle was located just above the left 'kick panel' under the dash of my truck. After you decide on a location & install the controller, just plug in the pigtail & follow the set-up instructions. I did have to hook up a ground wire for the pigtail. There are numerous places under the dash suitable for a ground; I elected to go thru the firewall & hook-up my ground near the battery
. I'm not a big guy (5' 9", 165#) so it was easy to find a location in my truck to mount the P3. Some larger folks have apparently had problems finding a suitable location. I never use the little 'swing out pocket' on left side of my dash so I mounted the P3 below that. It's within easy reach for the manual control, easily visible, & most important not in my way. The P3 is a very compact unit. If you're my size or not much bigger, a similar location should work for your 2015 Tacoma...
Here's mine, please excuse the mess -