engine TOYOTA PRIUS 2001 Service Repair Manual

CHASSIS ± STEERING
182CH68
Rear Wheel
Speed SensorsBrake ECU
Torque Sensor Signal 1
Torque Sensor Signal 2
EMPS
ECUMeter ECU
Gateway ECUDLC3
Display ECU
Multi-information
Display
123
EMPS (Electric Motor-assisted Power Steering)
1. General
In accordance with sensor information such as that provided by the rear wheel speed sensors, the torque sen-
sor that is mounted on the steering gear, and the EMPS ECU determines the direction and the force of the
power assist and actuates the DC motor that is mounted on the steering gear to provide power assist to the
steering effort.
The EMPS in the Prius the following features:
This system can provide power assist even when the engine is stopped.
This system offers excellent fuel economy characteristics because power assist is provided by the DC mo-
tor that is mounted on the steering gear, and this motor consumes energy only when power assist is re-
quired.
Unlike the conventional hydraulic power steering system, this system excels in serviceability because it
does not require pipes or the power steering fluid.

System Diagram 

BODY ± LOW VIBRATION AND LOW NOISE BODY
182BO09
182BO10
: Roof Silenser Pad
Foamed Urethane
Sponge
: Foamed Seal Material
: Felt
Dash Panel Silencer
Floor Silencer (RSPP)
:
136
LOW VIBRATION AND LOW NOISE BODY
1. General
Effective application of vibration damping and noise suppresant materials reduces engine and road noise.
2. Sound Absorbing and Vibration Damping Materials

Adoption of the dash panel silencer made the reduction of the engine and road noise and improved the
quietness in the compartment.

Foamed urethane sponge, foamed seal material, felt and roof silencer pad are applied onto the roof panel
and pillars to reduce wind and road noise.

The adoption of the floor silencer realized the reduction of the engine and road noise. Also, the adoption
of RSPP (Recycled Sound Proof Products) for raw material realized the improvement of recylability.

BODY ± AERODYNAMICS
182BO12
182BO13
Front Fairing Rear Fairing137
AERODYNAMICS
DESCRIPTION
To improve aerodynamic performance, the following measures have been taken.

The shapes of the front pillar, outside rear view mirror, and the front windshield glass have been optimized
to achieve a smooth air flow.

The height and the shape of the front bumper have been optimized in order to rectify the airflow under the
floor and along the body sides.

The shapes of the engine undercover, fuel tank bottom surface, and the rear floor bottom surface have been
optimized to achieve a smooth underbody air flow.

A front and rear fairings are provided to smooth out the airflow around the tires and reduce the air resis-
tance while the vehicle is in motion.

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 ± AIR CONDITIONING 152
AIR CONDITIONING
DESCRIPTION
The air conditioning system in the Prius has the following features:
Both heating and demisting performances are realized by adopting performances are realized by adopting
the 2-way flow heater type air conditioning unit.
A multi-tank, super-slim structure evaporator has been adopted.
An automatic air conditioning system which provides enhanced air conditioning comfort according to the
occupant's senses has been adopted.
A semi-center location air conditioning unit, in which the evaporator and heater core are placed in the ve-
hicle's longitudinal direction, has been adopted.
A compact, high-performance scroll compressor with oil separator has been adopted.
The heat exchange efficiency has been improved through the adoption of the sub-cool condenser.
This condenser is integrated with the radiator to minimize the space they occupy in the engine compart-
ment.
A compact, lightweight, and highly efficient straight flow (full-path flow) aluminium heater core has been
adopted.
This heater core is integrated with a PTC (Positive Temperature Coefficient) heater, which excels in heat-
ing performance.
PTC heaters have been provided in the air duct at the footwell outlet in front of the air conditioning unit.
However, air conditioning without the PTC heaters is offered as an option on the U.S.A. models.
An electrical water pump with a bypass valve that provides a stable heater performance even if the engine
is stopped due to a function of the THS (TOYOTA Hybrid System) has been adopted.
A clean air filter that excels in removing pollen and dust is standard equipment.

BODY ELECTRICAL ± AIR CONDITIONING
182BE17
PTC Heaters
182BE18
ALT AM1Ignition
Switch
HTR
MAIN
PS
HTR1PTC
HTR1PTC
HTR2
Battery
Heater Core
Integrated
PTC HeaterPTC Heaters
IG
HTR0
Air
Conditioning
ECU
HTR2
GNDMPX
IDH
Switch Signals from
Heater Control Panel
ECM
Body
ECU
Converter
Ambient
Temperature Sensor
Engine Coolant
Temperature Sensor
156
PTC heaters have been provided in the air
duct at the footwell outlet in front of the air
conditioning unit. However, air condition-
ing without the PTC heaters is offered as an
option on the U.S.A. models.
This PTC heater, which is a honeycomb-
shaped PTC thermistor, directly warms the
air that flows in the duct.

Wiring Diagram 

BODY ELECTRICAL ± AIR CONDITIONING
163BE17
Inner FinAntibacterial Agent
Nylon Layer
Chromate Layer
Aluminum
Matrix
182BE48
ModulatorMulti-Flow Condenser
Condensing Portion
Gaseous Refrigerant
Liquid Refrigerant
Super-Cooling Portion 158
Evaporator
By placing the tanks at the top and the bottom of the evaporator unit and by adopting an inner fin construc-
tion, the heat exchanging efficiency has been improved and the evaporator unit's temperature distribution
has been made more uniform. As a result, it has become possible to realize a thinner evaporator construction.
Furthermore, the evaporator body has been coated with a type of resin that contains an antibacterial agent
in order to minimize the source of foul odor and the propagation of bacteria.
2. Condenser
The Prius has adopted sub-cool condenser in which a multi-flow condenser (consisting of two cooling por-
tions: a condensing portion and a super-cooling portion) and a gas-liquid separator (modulator) have been
integrated. This condenser has adopted the sub-cool cycle for its cooling cycle system to improve the heat
exchanging efficiency.
This condenser is integrated with the radiator to minimize the space they occupy in the engine compartment.
For details, see page 54 in the Engine Cooling System Section.
Sub-Cool Cycle
In the sub-cool cycle of the sub-cool condenser that has been adopted, after the refrigerant passes through
the condensing portion of the condenser, both the liquid refrigerant and the gaseous refrigerant that could
not be liquefied are cooled again in the super-cooling portion. Thus, the refrigerant is sent to the evaporator
in an almost completely liquefied state.

BODY ELECTRICAL ± AIR CONDITIONING
165BE26165BE25
Discharge Port
Discharge Service Port
Pipe
Oil Discharge Hole
Shutter
Oil Storage Chamber
Discharge ValveRefrigerant and
Compressor OilRefrigerant
Compressor
Oil
182BE20182BE19
Flow of Coolant
Bypass Valve
Water Pump OFF
(Engine ON)Bypass Valve
Water Pump ON
(Engine OFF)Flow of Coolant163
2) Construction and Operation
The refrigerant gas that is discharged from the discharge port flows by rotating around the cylindrical
pipe in the oil separator. At this time, the centrifugal force that is created during the rotation separates
the refrigerant gas and the compressor oil due to the difference in their specific gravity. The refrigerant
gas with the lighter specific gravity passes through the inside of the pipe and travels from the discharge
service port to the outside of the compressor. The compressor oil with the heavier specific gravity is dis-
charged through the oil discharge hole in the shutter and is stored in the oil storage chamber. Then, the
compressor oil is fed again into the compressor and circulates inside the compressor.
4. Water Pump (For Air Conditioning)
An electrical water pump with a bypass valve that provides a stable heater performance even if the engine
is stopped due to a function of the THS has been adopted.
When the engine is running, this water pump ceases its operation and opens the bypass valve to minimize
the flow resistance of the coolant that is pumped by the engine water pump.

BODY ELECTRICAL ± AIR CONDITIONING
182BE22
Air
Conditioning
ECUBEAN
ECM
Room Temper-
ature SensorEvaporator Tem-
perature SensorSolar SensorAmbient Tem-
perature SensorEngien Coolant
Temperature Sensor
182BE23
Ambient Temperature Sensor165
6. Air Conditioning ECU
General
An automatic control type air conditioning has been adopted. This system uses an air conditioning ECU
to perform the calculation of the required outlet air temperature control, temperature control, blower con-
trol, air inlet control, air outlet control, and compressor control.
The information that is necessary for effecting the controls are the signals from the room temperature
sensor, evaporator temperature sensor, and solar sensor that are directly transmitted to the air condition-
ing ECU, and the signals from the ambient temperature sensor and the engine coolant temperature sensor
that are transmitted via the ECM. These signals are calculated by the air conditioning ECU to effect the
proper control.

System Diagram 
Sensors
1) Ambient Temperature Sensor
The ambient temperature sensor has been pro-
vided on the left, in front of the condenser.
The signals from this sensor are transmitted to
the air conditioning ECU via the ECM.