Toyota PRIUS Manual page 377

 Sounds and vibrations caused by the ABS, brake assist, VSC and TRC
A sound may be heard from the engine compartment when the hybrid

system is started, just after the vehicle begins to move, if the brake pedal
is depressed forcefully or repeatedly, or 1-2 minutes after the hybrid sys-
tem is stopped. This sound does not indicate that a malfunction has
occurred in any of these systems.
 Any of the following conditions may occur when the above systems are
operating. None of these indicates that a malfunction has occurred.
• Vibrations may be felt through the vehicle body and steering.
• A motor sound may be heard after the vehicle comes to a stop.
• The brake pedal may pulsate slightly after the ABS is activated.
• The brake pedal may move down slightly after the ABS is activated.
EPS operation sound

When the steering wheel is operated, a motor sound (whirring sound) may
be heard. This does not indicate a malfunction.
 Reduced effectiveness of the EPS system
The effectiveness of the EPS system is reduced to prevent the system from
overheating when there is frequent steering input over an extended period of
time. The steering wheel may feel heavy as a result. Should this occur,
refrain from excessive steering input or stop the vehicle and turn the hybrid
system off. The EPS system should return to normal within 10 minutes.
 Electric power steering system warning light (warning buzzer)
P. 566
PRIUS PHV_OM_OM47831E_(EE)
2-4. Using other driving systems
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