What else is needed for a 2010 Toyota Highlander that was prewired for towing?

I installed a wiring harness from the prewired connection found in the rear driver's side compartment and a fuse in the 'towing' slot in the fuse box, but the trailer lights still do not work. The lights do work when I hitch the trailer to my truck.What else is needed for a 2010 Toyota Highlander that was prewired for towing?
the easist thing i can think of is to make sure its grounded some already are grounded to the body especially if its preinstalled so you might want to remove the ground that you installed or add one that you didnt



try and see if that works



also check if your getting power at the lights after you hook it up using a volt meter and if your not getting power theres your problem you just have to figure out where your losing the powerWhat else is needed for a 2010 Toyota Highlander that was prewired for towing?
it is possible there is another fuse not installed. check "fuses" in the owners manual.