2001 TOYOTA PRIUS Service Repair Manual

THS (TOYOTA HYBRID SYSTEM)
182TH33
31
± REFERENCE ±
The MG1 and the MG2 are generally shut down when the shift lever is in the N position.
However, the shut-down function is canceled under the following exceptions:

During driving, if the brake pedal is depressed and a wheel locks up, the ABS is activated. After this, low
torque is requested from the MG2 to provide supplemental power in order to restart the rotation of the wheel.
Even if the shift lever is in the N position at this time, the shut-down function is canceled to allow the wheel
to rotate. After the wheel rotation has been restarted, the system resumes its shut-down function.

When the vehicle is driven in the D or B position and the brake pedal is depressed, the regenerative brake
operates. At this time, as the driver moves the shift lever to the N position, the brake hydraulic pressure in-
creases while the request torque of the regenerative brake decreases gradually so as not to create a sluggish
brake feel. After this, the system effects its shut-down function.
When any of the conditions described below is pres-
ent, the message prompt as shown appears in the
multi information display, accompanied by the illu-
mination of the master warning light and the continu-
ous sounding of the buzzer.

The ªREADYº light is illuminated, the shift lever
is in the N position, and the HV battery is dis-
charged.

The ªREADYº light is illuminated, the shift lever
is in the N position, and the driver's door is open.

The ªREADYº light is illuminated, the parking brake is engaged, the shift lever is in the B or D position, and
the driver's door is open.

THS (TOYOTA HYBRID SYSTEM)
182TH22
1. READY Light
2. Output Control
Warning Light 3. Master Warning Light
4. Malfunction Indicator light 5. Discharge Warning Light
6. EMPS Malfunction
Warning Light7. HV Battery Warning Light
8. Hybrid System
Malfunction Warning
Light 32
INDICATOR AND WARNING LIGHT
The warning lights of the Prius are different from those on conventional vehicles. Inspection and repair
should be performed while referring to the troubleshooting section in the 2001 Prius repair manual
(RM778U).

Center Meter 
Multi Information Display 
1. READY lightTurns on when the ignition switch is turned to START to indicate that the ve-
hicle is ready to drive.
2. Output control
warning lightTurns on when the remaining HV battery charge becomes insufficient at R
range or when there is an abnormal temperature rise in the HV battery due
to continuous driving under heavy loads. It may also light when the HV bat-
tery temperature is low (after starting at low temperatures). The hybrid sys-
tem output is limited while this light is on.
Travel at reduced speeds (avoid sudden acceleration) while the light is lit.
3. Master warning
lightTurns on with buzzer sounding by linked operation with warning lights ª6º
to ª8º on the multi center display.
4. Malfunction
indicator lightTurns on when there is a malfunction in the engine control system.
5. Discharge warning
lightTurns on when there is a malfunction in the 12 V charging system (converter
assembly).
If it turns on together with the master warning light and hybrid system
warning light, check the diagnostic code.
6. EMPS malfunction
warning lightTurns on when there is a malfunction in the EMPS control system.
7. HV battery warning
lightTurns on when the HV battery is discharged to the lower limit.
8. Hybrid system
warning lightTurns on when a malfunction in MG1, 2, inverter, HV battery or HV ECU
is detected.

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.