The Blind Spot Monitor is a system that has 2 functions;
These functions use same sensors.

RCTA function: When a vehicle approaching from the right or left at the rear of the vehicle is detected, both outside rear view mirror indicators will flash.
Turning the BSM function/RCTA function on/offToyota CH-R Service Manual > Can Communication System: Radio Receiver Assembly Communication Stop Mode
DESCRIPTION
Detection Item
Symptom
Trouble Area
Radio Receiver Assembly Communication Stop Mode
Any of the following conditions are met:
Communication stop for "Display and Navigation (AVN)" is indicated
on t ...
Toyota CH-R Service Manual > Front Door Speaker: Installation
INSTALLATION
CAUTION / NOTICE / HINT
HINT:
Use the same procedure for the RH and LH sides.
The procedure listed below is for the LH side.
PROCEDURE
1. INSTALL FRONT NO. 1 SPEAKER ASSEMBLY
(a) Engage the claw and guide to temporarily install the front No. 1
spea ...