This happened to me in my Model Y (no FSD Beta, or enhanced autopilot) a couple days ago. Driving on highway 167 north between Puyallup and Renton. Daytime, overcast, no rain, perfect visibility. This is a fully divided freeway with a constant speed limit of 60 (which the car picked up correctly). Traffic was light to medium.
I was using TACC (just speed control, not autosteer), and set the max speed to 69, which roughly matched the speed of the traffic around me. Suddenly, the car changed the max speed to 65, and immediately and noticeably slowed to 65. The detected speed limit was still 60. I thought this was odd, and then I used the right scroll wheel to up the top speed to 69 again. A few minutes later, it did the same thing again, but then about 10 seconds later, before I did anything, it raised it back to 69. And another two or so minutes later, it did it a third time, lowering the top speed to 65, then 10 or so seconds later, raised it back to 69 by itself. This time I saw it go both down and up on the screen. After that, it didn't happen again for the rest of the drive, although I didn't have TACC on for that much longer (maybe 10 minutes). The 4 mph change wasn't enough to be a danger, but it was enough to sort of startle me.
There were no audible notifications, and no message on the touch screen. The detected speed limit stayed at 60 the whole time.
I don't understand what was triggering this behavior. Is this ever to be expected? It has never happened before.
I was using TACC (just speed control, not autosteer), and set the max speed to 69, which roughly matched the speed of the traffic around me. Suddenly, the car changed the max speed to 65, and immediately and noticeably slowed to 65. The detected speed limit was still 60. I thought this was odd, and then I used the right scroll wheel to up the top speed to 69 again. A few minutes later, it did the same thing again, but then about 10 seconds later, before I did anything, it raised it back to 69. And another two or so minutes later, it did it a third time, lowering the top speed to 65, then 10 or so seconds later, raised it back to 69 by itself. This time I saw it go both down and up on the screen. After that, it didn't happen again for the rest of the drive, although I didn't have TACC on for that much longer (maybe 10 minutes). The 4 mph change wasn't enough to be a danger, but it was enough to sort of startle me.
There were no audible notifications, and no message on the touch screen. The detected speed limit stayed at 60 the whole time.
I don't understand what was triggering this behavior. Is this ever to be expected? It has never happened before.
