While traveling North on [XXX] in N. Texas, congested roadway at the time, had to come to an abrupt stop because a vehicle in front of me suddenly hit their brakes. The forward collision system worked as it should, the icon popped up on the display and the vehicle started braking. One morning as I prepare to pull out of my driveway, vehicle facing North, the forward collision icon is on the dash with a diagonal line through it. I wasn’t sure what that meant so I looked it up and it meant that something was blocking the sensor. Happened to be dirt from recent dust storm with rain so there was a spot that the windshield wipers cant reach therefore the sensor was blocked. Cleaned it off no more icon on the dash. Traveling West on [XXX] in West Texas, the icon appears on the dash once again with the diagonal line through it. The closest vehicle to me was around 3 quarters of a mile in front of me so there was no danger of a front collision. I noticed that as I passed under an overpass the icon disappeared but as soon a I exited the overpass the icon reappeared. Once the sun reached a certain point in the horizon when setting, the icon went off for good. This has also happened when driving in town and I am heading home form work. traveling West into the setting sun. Without a doubt if the sun is in a certain point on the horizon when setting, it will block or blind that sensor however you wish to describe it, and that safety feature will be temporarily inoperable until the sun sets lower. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)