The 4 prong plug on the rear of a RX350 for trailer wiring,

I have the same problem. Did you find out anything?

I have the same issue as well, have you learned anything regarding the issue?

rx 350s without tow package require a tow relay in order for the 4 pin harness to operate. 2010 to 2015 part number is 81985-wy010. The location is behind the passenger side taillight

I bought the part 81985-WY010 for my RX-350 but can't find where to connect it. Do I have to remove the tail light access cover on the passenger side? I see a black plastic box attached to the rear quarter panel and accessible from the trunk but don't know how to release the tabs to see if it goes in there. I don't want to break them.

there is a module buried somewhere in the car that generates tow harnes turn signal, stop light, and running light signals. If you did not buy the OEM tow package with the car, you at the very least need to add that controller.