Adding my 2 cents here. Just installed a Tekonsha (Prodigy) Primus IQ to my '03 and it was a breeze. Finding the factory connector was really easy after removing the lower dash panel and knee brace. That takes about five minutes and you don't have to get down on your back and feel around in the dark. Removing those two items, plus the dash cap, made it super easy to snake the wires to the ashtray cubby which is where I installed the controller. Best part of the deal was going out to Stevinson Toyota where I had ordered the Tundra connector from - $42 retail - $30 my discount price. When I told Derek, my parts guy there, what I was doing, he said "You don't want the OEM connector, you want this Tekonsha connector instead" which he had hanging on a rack right there. He was right, of course, as it was $12 retail and $9, plus tax, and it fit perfectly, connecting to the plug behind the dash and the back of the controller. Tekonsha part # is 3040-P and it was made specifically for the Toyota connector with plenty of lead length. Attached the ground wire from the harness to the upper left knee brace bracket. Everything works perfectly. Yup, Bob's your uncle and thanks Mud for making this a less than one banana job that took less than an hour.
