When towing a trailer that weighs over 3000 lbs, a brake controller is required.  My new Tacoma  doesn’t have one.  My last Tacoma didn’t either, but the RV dealership put one on in about 15 minutes because the wiring harness was already there. 

Toyota decided to stop doing that.  Now they sell Tacomas with a tow package, but no brake controller or provision to install a brake controller. 

A few people have instructions online for the installation, but none of them match up.  It’s a research project.  I’m going to wait for a couple of weeks until Tech Support at the company is back from vacation.