Toyota prius Owner's Manual page 510

5-2. Steps to take in an emergency
Warning message
(Flashes 3
times)
*
: Rear passenger's seat belt buzzer:
The rear seat belts reminder sounds to alert the rear passenger that his/her
seat belt is not fastened. The buzzer sounds for 30 seconds after the vehicle
has reached a speed of at least 20 km/h (12 mph). Then, if the seat belt is
still unfastened, the buzzer will sound in a different tone for 90 more sec-
onds.
 Warning message in radar cruise mode (if equipped)
In the following cases, the warning message may not be displayed even if
vehicle-to-vehicle distance decreases:
 When your vehicle and the vehicle ahead are traveling at the same
speed or the vehicle ahead is traveling more quickly than your vehicle.
 When the vehicle ahead is traveling at very low speed.
 Immediately after cruise control speed is set.
 At the instant the accelerator pedal is depressed.
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PRIUS_OM_OM47871E_(EE)
Details
EV drive mode has been auto-
matically canceled.
A buzzer also sounds.
The reason why EV drive
mode cannot be used is
shown (may not be shown in
some instances.)
Correction
procedure
Drive normally for a
short time.