Warning !If you buy the Rostra 250-1836 kit the directions tell you to buy Toyota part #45186-06230-C0. It will not fit ( that part# is for a Camry) .
I installed the Rostra cruise kit this morning in my 2012 4cyl automatic. Pretty straight forward for the most part. Other than the incorrect part number for the cruise stalk cover. The other aggravation for me was the illustration for removing the air bag. Either the illustration was not clear or incorrect . It took me a few minutes to figure out on a 2012 you pop off the small covers on the back of the steering wheel at 9 and 3 o'clock to access the two #30 Torx bolts.)
My kit came with two brown wires for the connection to the ECM. The correct wire has two ends exactly the same and will match the terminal on the ground wire, The incorrect wire has a tag with # 59b-05855 and the two terminals are different from each other. Make sure you pop up the terminal retainer( Fig 17) on the S8 and ECM connector otherwise they won't go in all the way and won't make a connection. When you look at the pin connection side of the connector you should be able to see the terminal through the pin hole.
Under the dash on the left side of the steering column you will see a metal bracket connecting to the dash with a 6mm hole in it. I used this for a ground I fastened the ground wire with a 6mm x 13mm bolt and nut.
When you run the wire(s) to ECM behind the glove box don't block the access to the cabin airfilter.
If it doesn't work double check your connections . At the ECM connector I had to reinsert the brown wire and carefully push it in with the point of an ice pick to get it in far enough to get a connection.