Toyota 2010 Prius Owner's Manual page 538

5-2. Steps to take in an emergency
Warning message
■
After changing the engine oil (U.S.A. only)
Make sure to reset the oil maintenance data. (→P. 428)
■
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.
516
Details
EV-Drive Mode cannot be
switched to.
A buzzer also sounds.
The EV-Drive Mode has been
automatically cancelled.
A buzzer also sounds.
Correction
procedure
Use the EV-Drive
Mode when it
becomes available.
Drive normally for a
short time.