I recently bought a BRAND NEW IS300h Premier from Lexus Leicester. As I started driving, I suddenly discovered that the speed limits it showed were TOTALLY wrong and bizarre. It showed the SL (Speed Limit) as 90 on a 30-mph road, certain areas it was 120 mph or even 140 at times. Then when I tried the Adaptive Cruise Control (ACC) it went OK and suddenly a heard a warning beep and I had to suddenly put the brake on to avoid a collision with the car in front.
The car was booked in and initially they said that a part needs to be ordered and after a few days I was informed that there is nothing wrong and that the ACC stops working below 30mph.
I had a LS600 which worked perfectly and the car would stop if the car in front stopped. My daughter has a Lexus NX and it works fine in that car too