Toyota/Lexus has the capability to produce cars that don't need tech like failing sensors, Brakes, Buzzers and Ding Dongs and have a superior car. The EPA/Government has there way with manufacturers, I don't like that...
There is a clean out on the rack with a filtering screen that should be removed and cleaned. Search this forum, There is much discussion about this . The clean out has a large Hex head ( If I remember correctly )
The calipers hold the pads, The pins guide the calipers from standing to compression and back to standing, There are no holes in the pads that the pins go through.