The following is a description of the LRSM (light rain sensor module) system. It 'sees' the refraction of water droplets on the windshield glass.
You may need the inside rear view mirror assembly with the connector for the installation?
Is there a +12 volt power, a ground & an Orange LIN bus wire at the rearview mirror?
If not, it would need wires run up behind the left A-pillar trim piece and over the headliner to the LRSM.
Does BCM C6-cavity #14 have a terminal & Orange wire in it?