TOYOTA PRIUS 2001 Service Repair Manual

THS (TOYOTA HYBRID SYSTEM)
182CH05
Stator
Rotor
Speed Sensor (Resolver)
MG1
182CH04
Stator
Rotor
Speed Sensor (Resolver)
MG2
182TH07
N.m
350
300
250
200
150
100
50
0
01000 30002000 50004000 60000 20 40
30
10 kW
Torque
Engine Speed (rpm)Output
Torque
Output
33
MG1 AND MG2 (MOTOR GENERATOR NO.1 AND NO.2)
DESCRIPTION
Both the MG1 and the MG2 are compact, lightweight, and highly efficient alternating current permanent
magnet synchronous type.
Serving as the source of supplemental motive force that provides power assistance to the engine as needed,
the electric motor helps the vehicle achieve excellent dynamic performance, including smooth start-offs
and acceleration. When the regenerative brake is activated, MG2 converts the vehicle's kinetic energy into
electrical energy, which is then stored in the HV battery.
MG1 recharges the HV battery and supplies electrical power to drive MG2. In addition, by regulating the
amount of electrical power generated (thus varying the generator's rpm), MG1 effectively controls the
continuously variable transmission function of the transaxle. MG1 also serves as the starter to start the
engine.

MG2 Specifications 
TypePermanent Magnet
Motor (1CM)
Rated voltage [V]273.6
Maximum output [kW] (rpm)33 / (1040
5600)
Maximum torque [N.m (kgf.m) (rpm)350 / (0
400)
Amperage at maximum torque [A]351
Cooling systemWater-cooled

Performance Curve 

THS (TOYOTA HYBRID SYSTEM)
182TH29
Rotational
Magnetic FieldU PhaseStator Coil
Rotor
Repulsion
W Phase V Phase
: From inverter
: Connected internally in the motor
Attruction
182TH09
Magnetized Side
Coil A
Coil B
Coil C Speed Sensor
(Resolver)Output Side
182TH10
Inverter Power Cable HV Battery
Junction
BlockPortion routed through
the center floorAuxiliary
Battery
Under-
the-Floor
Reinforcement
12 V
Power Cable
Voltage 
Power Cable
Voltage

34
1. Permanent Magnet Motor
When a three-phase alternating current is passed
through the three-phase windings of the stator
coil, a rotational magnetic field is created in the
electric motor. By controlling this rotating mag-
netic field according to the rotor's rotational posi-
tion and speed, the permanent magnets that are
provided in the rotor become attracted by the ro-
tating magnetic field, thus generating torque.
The generated torque is for all practical purposes
proportionate to the amount of current, and the
rotational speed is controlled by the frequency of
the alternating current.
Furthermore, a high level of torque, all the way to
high speeds, can be generated efficiently by prop-
erly controlling the rotating magnetic field and the
angles of the rotor magnets.
2. Speed Sensor (Resolver)
This is an extremely reliable and compact sensor
that precisely detects the magnetic pole position,
which is indispensable for ensuring the efficient
control of MG1 and MG2.
The sensor's stator contains 3 coils as illustrated, and
output coils B and C are electrically staggered 90 de-
grees. Because the rotor is oval, the distance of the
gap between the stator and the rotor varies with the
rotation of the rotor. Thus, by passing an alternating
current through coil A, output that corresponds to the
sensor rotor's position is generated by coils B and C.
The absolute position can then be detected from the
difference between these outputs.
In addition, the amount of positional variance
within a predetermined time is calculated by the
HV ECU, thus enabling this sensor to be used as
an rpm sensor.
3. Power Cable
The power cable is a high-voltage, high-amperage
cable that connects the HV battery with the inverter,
and the inverter with MG1 and MG2. Starting from
the connector at the left front of the HV battery lo-
cated in the luggage compartment, the power cable
is routed under the rear seat, through the floor panel,
along the under-the-floor reinforcement, and con-
nects to the inverter in the engine compartment. A
shielded cable is used for the power cable in order to
reduce electromagnetic interference.
The 12 V  wiring of the auxiliary battery also
follows the same route.
For identification purposes, the high-voltage wir-
ing harness and connectors are color-coded
orange to distinguish them from those of the ordi-
nary low-voltage wiring.

THS (TOYOTA HYBRID SYSTEM)
182TH26
Inverter
Converter
182TH15
Inverter
HV
Battery
Ignition Signal
Ground
Voltage
Detection
Circuit
Voltage
Detection
Circuit
Bridge Circuit for MG2
Amperage
Sensor
Signal Processor /
Protective Function Processor
Bridge Circuit for MG1
Amperage
Sensor
MG2
HV ECU
MG1
182TH27
Reservoir Tank
Radiator
Water Pump35
INVERTER
1. General
The inverter is an electric power converter that
converts the direct current of the Hybrid vehicle's
high-voltage battery (DC 273.6 V) and the alter-
nating current of the MG1 and MG2.
Consisting of 2 three-phase bridge circuits for
MG1 and MG2, respectively, and each containing
6 power transistors, the inverter converts direct
current and three-phase alternating current. The ac-
tivation of the power transistors is controlled by the
HV ECU. In addition, the inverter transmits in-
formation that is needed for current control, such as
the output amperage or voltage, to the HV ECU.
Together with MG1 and MG2, the inverter is
cooled by the dedicated radiator of the coolant
system that is separate from that of the engine.
2. System Diagram
3. Cooling System
A cooling system via water pump for the inverter
and MG1, 2 has been added.
The HV ECU controls the water pump with cool-
ant temperature.
It is separated with the engine cooling system.

THS (TOYOTA HYBRID SYSTEM)
182TH26
Inverter
Converter
182TH17
F. L
MAINF.L DCDC12 V

Output
Auxiliary
Battery S34B20
Shielded 12 VInverter
SDC273.6 V
DC / DC Converter
Input Filter
20 V
Converter Control Circuit
HV ECU A / C ECUIG
IDH NODD 36
CONVERTER
1. General
The power source for auxiliary equipment of the
vehicle such as the lights, audio system, and the air
conditioner cooling fan, as well as the ECUs, is
based on a 12 V system. Because the THS genera-
tor outputs at 273.6 V, the converter is used to
transform the voltage from DC273.6 V to DC 12
V in order to recharge the auxiliary battery. The
converter is installed on the underside of the in-
verter.
2. Operation

The DC273.6 V input is initially converted into alternating current by the transistor bridge circuit and
transformed into a low voltage by the transformer. After this, the current is rectified, smoothed (into direct
current) and converted into DC12 V.

The voltage at the positive terminal of the auxiliary battery is monitored by the converter and is maintained
at a constant level. Consequently, the voltage of the auxiliary battery is unrelated to the engine rpm (even
if the engine is stopped) and to the auxiliary equipment (output current of converter).

THS (TOYOTA HYBRID SYSTEM)
182TH34
Battery Pack Upper Case
Service Plug
SMR
(System Main Relay)Battery ECU
HV Battery Module37
HV BATTERY
DESCRIPTION
The sealed nickel metal hydride (Ni-MH) battery technology has been further evolved in the newly devel-
oped HV battery that offers features such as high power density, lightweight, and longevity, that are specifi-
cally designed to match the characteristics of the THS. Because the THS effects charge / discharge control
to maintain a constant level of SOC (state of charge) while the vehicle is operating normally, it does not rely
on the use of external rechargers.
In the battery area, six 1.2-volt cells are connected in series to form one module. A total of 38 modules are
divided into two holders and connected in series. Thus, the HV battery containing a total of 228 cells has a
rated voltage of 273.6 V.
The electrode plates in the HV battery are made of materials such as porous nickel and metal hydride alloy.

THS (TOYOTA HYBRID SYSTEM)
Battery Voltage for Each
Module
HV Battery Temp. Sensor
Temp. Sensor (Circumference)
Amperage sensor
A / C Signal
Battery ECU
A / C ECU
HV Battery Cooling Fan
HV ECU
Amperage Signal
Total Voltage Signal
Charge or Discharge Signal
DiagnosisData Link Connector 3
182TH11
HV Battery
SMR2
Battery Module
(7.2 V x 19)
Service Plug
High-Voltage Fuse
Battery Module
(7.2 V x 19)
SMR3
Resistor SMR1
38
HV BATTERY CONTROL SYSTEM
DESCRIPTION
To maintain the battery at a proper SOC (state of charge), and to ensure safety in the event that the HV battery
malfunctions, the battery ECU features the following control functions:

System Diagram 
CONSTRUCTION
The HV battery, battery ECU, and SMR (sys-
tem main relay), are enclosed in a single case
and placed in the luggage compartment behind
the rear seat to make more effective use of ve-
hicle space.
In the battery area, six 1.2-volt cells are con-
nected in series to form one module. A total of
38 modules are connected in series.
Thus, the HV battery containing a total of 228
cells has a rated voltage of 273.6 V.
A service plug that shuts off the circuit is pro-
vided in the middle of the 38 modules. Before
servicing any portion of the high-voltage cir-
cuit, make sure to remove the service plug. For
further details, refer to the 2001 Prius Repair
Manual (Pub No. RM778U).

THS (TOYOTA HYBRID SYSTEM)
182TH12
SOCExample of change in SOC
Upper SOC control limit
Control regionTarget SOC
control
Lower SOC control limit
Time
Overcharged region
Overcharged region
39
1. Battery ECU
The battery ECU provides the following functions.
SOC (state of charge) Control
While the vehicle is in motion, the HV battery
undergoes repetitive charging / discharging
cycles, as it becomes discharged by the MG2
during acceleration and charged by the regenera-
tive brake during deceleration. The battery ECU
outputs charge / discharge requests to the HV
ECU so that the SOC can be constantly main-
tained at a center level, by estimating the charg-
ing / discharging amperage.
Cooling Fan Control
To ensure the HV battery's performance considering the heat that is generated in the HV battery during
charging and discharging, the battery ECU controls the operation of the cooling fan.
HV Battery Malfunction Monitoring
This function includes the monitoring of the temperature and the voltage of the battery via the battery ECU.
If a malfunction is detected, the battery ECU protects the HV battery by restricting or stopping the charging
and discharging of the HV battery. In addition, this function illuminates the warning light, outputs DTCs
(Diagnostic Trouble Codes), and stores them in memory. For further details on the DTCs, refer to the 2001
Prius Repair Manual (Pub No. RM778U).

THS (TOYOTA HYBRID SYSTEM)
182TH11
HV Battery
SMR 2
SMR 1
Battery Module
(7.2 V x 19)
Resistor
Service Plug
High-Voltage Fuse
Battery Module
(7.2 V x 19)
SMR 3
182TH30
Service Plug 40
2. SMR (System Main Relay)
The SMR is a relay that connects and disconnects
the power source of the high-voltage circuit upon
receiving a command from the HV ECU. A total
of 3 relays, one for the negative side, and two for
the positive side, are provided to ensure proper op-
erations.
At the time of connection, SMR1 and SMR3 are
turned ON; after this, SMR2 is turned ON and
SMR1 is turned OFF. By allowing the controlled
current via the resistor to pass through initially in
this manner, the circuit is protected against rush
current.
At the time of disconnection, SMR2 and SMR3
are turned OFF in that order, and the HV ECU ver-
ifies that the respective relays have been properly
turned OFF.
3. Service Plug
By removing the service plug before performing any inspection or service, the high-voltage circuit is shut
off at the intermediate position of the HV battery, thus ensuring safety during service.
The service plug assembly contains a reed switch for interlock. Lifting the clip lock up turns OFF the reed
switch, which shuts off the SMR. However, to ensure safety, make sure to turn OFF the ignition switch before
removing the service plug. For further details on how to handle the service plug, refer to the 2001 Prius Repair
Manual (Pub No. RM778U). The main fuse for the high-voltage circuit is provided inside of the service plug
assembly.

THS (TOYOTA HYBRID SYSTEM)
182TH20
Cooling FanAir Intake
HV Battery Exhaust Duct No.2Exhaust Duct No.141
HV BATTERY COOLING SYSTEM
DESCRIPTION
When the temperature of the HV battery rises, the battery ECU executes a command to cause the cooling fan
to operate from OFF to LO, MID and HI speeds. However, if the air conditioning is being used at that time
to cool the vehicle's interior, and if there is still some margin left in the temperature of the HV battery, the
battery ECU keeps the fan OFF or running at LO speed, thus giving priority to the air conditioning.
The air intake for the cooling fan is located above the package tray trim. If an object (such as clothing) is
placed over this area, the HV battery might not be able to cool sufficiently, which could cause the output con-
trol warning light to illuminate.
CONSTRUCTION
This system feature a cooling fan which is driven by DC motor.

Specifications 
TypeSirocco Fan
Fan Size Dia x H mm (in.)100 x 40 (4.0 x 1.6)
Motor TypeDC Motor
Lo50
Air Flow Volume m3/hMid100
Hi150
Power Consumption W60
The operation of the cooling fans is controlled by the signals that are output by the battery ECU, which
monitors the temperature of the HV battery.

THS (TOYOTA HYBRID SYSTEM)
182TH21
Lead-calcium Alloy 42
AUXILIARY BATTERY
DESCRIPTION
The shielded, maintenance-free 12V battery (S34B20L) for the Prius is used.
Battery fluid is filtered into separators in order to reduce hydrogen gas released which occurs when the battery
is charged.
Therefore, battery fluid does not need to be replaced, as long as the specified battery is used.
HV IMMOBILISER SYSTEM
The HV immobiliser system has been designed to prevent the vehicle from being stolen. This system uses a
ECM that stores the ID code of the authorized ignition key. If an attempt is made to start the HV system using
an unauthorized key, the ECM prohibit fuel delivery and ignition, effectively disabling the engine.