When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
If it's on the kick panel beside the driver left foot, I suspect it is to turn on/off an aftermarket remote starter or possibly security device. If you have a small, black thing with a wire sticking out both sides of it on the windshield and up by the mirror, then it's the same as I found on my '14. For some reason that remote starter also (at least on mine) also permits remote start from the key fob but remote start is not on the original build list. If you did not get a separate fob (mine came with a couple of "Python" fobs...the precursor to "Viper") then try the remote start with the Lexus key fob. Personally I never use it as the car is kept in the garage during winter and it's never hot enough (yet!) up here to need to run AC before getting in so the remote is kept turned off.