2001 TOYOTA PRIUS Service Repair Manual

BODY ± ENHANCEMENT OF PRODUCT APPEAL
182BO16
Gas Pressure from
the Gas Generator
RackBobbinSeat Belt
Planetary Gear
Pinion GearClutch Mechanism
139
SEAT BELT
1. General

The front seats are provided with an electrical sensing type seat belt pretensioner and a seat belt force limit-
er. In the beginning of a collision, the seat belt pretensioner instantly pulls up the seat belt thus providing
the excellent belt's effectiveness in restraining the occupant.
When the impact of a collision causes the tension of the seat belt applied to the occupant to reach a predeter-
mined level, the force limiter restrains the tension, thus controlling the force applied to the occupant's chest
area.

In accordance with the ignition signal from the airbag sensor assembly, the seat belt pretensioner activates
simultaneously with the deployment of the SRS airbags for the driver and front passenger.

The passenger seats are provided with ALR (Automatic Locking Retractor) / ELR (Emergency Locking
Retractor) seat belts.
2. Seat Belt Pretensioner
General
The pretensioner mechanism mainly consists of a rack, pinion gear, planetary gear, clutch mechanism, and
a bobbin.
During the deployment of this pretensioner mechanism, the gas pressure from the gas generator pushes the
rack down and retracts the seat belt via the pinion gear, planetary gear, clutch mechanism, and bobbin.

BODY ± ENHANCEMENT OF PRODUCT APPEAL
174BO02
Energy Absorbing Shaft
Lock Sensor AssemblySeat Belt
Bobbin
Sleeve 140
3. Seat Belt Force Limiter
The seat belt force limiter mainly consists of an energy absorbing shaft, lock sensor assembly, bobbin, and
sleeve.
When the seat belt is pulled out at a rate that exceeds the specified acceleration rate, the ELR (Emergency
Locking Retractor) becomes activated, causing the lock sensor assembly to lock the energy absorbing shaft.
Because the bobbin on which the seat belt is attached is secured to the energy absorbing shaft via the sleeve,
the energy absorbing shaft becomes twisted. The twisting of the energy absorbing shaft causes the bobbin
to rotate and the seat belt to be pulled out, thus maintaining the tension that is applied to the seat belt.

BODY ELECTRICAL
BODY ELECTRICAL ± BATTERY AND MULTIPLEX COMMUNICATION SYSTEM
182BE01
: BEAN : UART
: AVC-LAN : Serial Data
Link
Brake ECU
HV ECU
Air Condi-
tioning ECU
Meter ECU
ECM
Body ECU
Display ECU
Audio
ComponentsGateway
ECU
Power Window
Master SwitchDoor Con-
trol ReceiverBattery ECU
141
AUXILIARY BATTERY
DESCRIPTION
All the body electrical systems and auxiliary equipment operate using the same 12 V battery used on ordinary
gasoline engine vehicles.
However, as the battery structure is different, Prius uses an exclusive battery. See page 42 in the THS (TOYOTA
Hybrid System) section for details of the auxiliary battery structure.
MULTIPLEX COMMUNICATION SYSTEM
DESCRIPTION
A multiplex communication system has been adopted for body electrical system control and to achieve
a slimmer wiring harnesses configuration.
BEAN (Body Electronics Area Network) has been adopted between the body ECU, ECM, meter ECU,
air conditioning ECU, and the gateway ECU. Furthermore, AVC-LAN (Audio Visual Communication-
Local Area Network) has been adopted between the display ECU and the audio components.
The conversion of communication signals between BEAN and AVC-LAN is performed by the gateway
ECU.
UART (Universal Asynchronous Receiver Transmitter), which performs unidirectional communication,
has been adopted between the body ECU and the power window master switch.
A serial data link has been adopted between the body ECU and the door control receiver. In addition, a
serial data link has been adopted between the ECM, HV ECU, brake ECU, and the battery ECU, which
pertain to the control of the hybrid system.

System Diagram 

BODY ELECTRICAL ± MULTIPLEX COMMUNICATION SYSTEM 142
SYSTEM OPERATION
1. General
The ECUs that pertain to the body electrical system perform the functions and system controls described be-
low.
Gateway ECU
Conversion of data between AVC-LAN and BEAN
Transmission of vehicle information to the display ECU, in order for it to be displayed on multi-informa-
tion display
Body ECU
Power window system control (Front, Rear passenger only)
Door lock control system control
Wireless door lock remote control system control
Theft deferrent system control
Daytime running light system control
Illuminated entry system control
Light auto turn-off system control
Seat belt warning system control
Key reminder system control
Diagnosis
Meter ECU
Meter control
Illumination and flashing control of indicator and warning lights
Sounding control of warning buzzer
Air Conditioning ECU
Air Conditioning control
ECM
Engine control
Diagnosis
Display ECU
Transmission and reception associated with audio and visual functions

BODY ELECTRICAL ± MULTIPLEX COMMUNICATION SYSTEM
182BE02
Display ECU
CPU
AV C - L A N
Transmis-
sion
Reception
ControlAVC-LAN
Transmis-
sion
Reception
CircuitAVC-LANGateway ECU
CPU
AVC-LAN
Transmis-
sion
Reception
CircuitCon-
version
ControlBEAN
Trans-
mission
Recep-
tion
Circuit
Audio
Components
BEAN
Body ECU Meter ECU
143
2. Gateway Function (Gateway ECU)
This multiplex communication system has adopted BEAN (Body Electronics Area Network) between the
body ECU, ECM, meter ECU, air conditioning ECU, and the gateway ECU, as well as AVC-LAN between
the display ECU and the audio components. Because the data configuration differs between BEAN and AVC-
LAN, their data must be converted in order for them to exchange each other's data. The conversion of com-
munication data is performed by the gateway ECU. As a result, it has become possible for a single commu-
nication line to transmit various types of information.