Toyota 2012 Prius Owner's Manual page 580

Warning message
■
Approach warning message
In the following instances, there is the possibility that the approach warning
will not activate even when the 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.
PRIUS PHV_OM_OM47818U_(U)
5-2. Steps to take in an emergency
Details
The fuel filler door has been
left open.
The charging port lid is open.
Correction
procedure
Tighten the fuel
tank cap and close
the fuel filler door.
Close the charging
port lid.
555
5