power steering TOYOTA PRIUS 2001 Service Repair Manual

*The titles given inside the components are the names of the terminals (terminal codes) and are not treated as being
abbreviations.
2001 PRIUS (EWD414U)
ABBREVIATIONS D
ABBREVIATIONS
The following abbreviations are used in this manual.
ABS = Anti±Lock Brake System
A/C = Air Conditioning
COMB. = Combination
DC = Direct Current
ECU = Electronic Control Unit
EMPS = Electric Motor Power Steering
ESA = Electronic Spark Advance
EVAP = Evaporative Emission
HV = Hybrid Vehicle
J/B = Junction Block
LH = Left±Hand
PTC = Positive Temperature Coefficient
R/B = Relay Block
RH = Right±Hand
SFI = Sequential Multiport Fuel Injection
SRS = Supplemental Restraint System
SW = Switch
TEMP. = Temperature
VSV = Vacuum Switching Valve
w/ = With
w/o = Without

2001 PRIUS (EWD414U)
SRS
NOTICE: When inspecting or repairing the SRS, perform the operation in accordance with the following precautionary
instructions and the procedure and precautions in the Repair Manual for the applicable model year.

Malfunction symptoms of the SRS are difficult to confirm, so the DTCs become the most important source of information
when troubleshooting. When troubleshooting the SRS, always inspect the DTCs before disconnecting the battery.

Work must be started after 90 seconds from when the ignition switch is turned to the ºLOCKº position and the
negative (±) terminal cable is disconnected from the battery.
(The SRS is equipped with a back±up power source so that if work is started within 90 seconds from
disconnecting the negative (±) terminal cable of the battery, the SRS may be deployed.)

When the negative (±) terminal cable is disconnected from the battery, the memory of the clock and audio system will be
canceled. So before starting work, make a record of the contents memorized in the audio memory system. When work is
finished, reset the audio systems as they were before and adjust the clock. To avoid erasing the memory in each
memory system, never use a back±up power supply from outside the vehicle.

Before repairs, remove the airbag sensor if shocks are likely to be applied to the sensor during repairs.

Do not expose the steering wheel pad, front passenger airbag assembly, side airbag assembly, seat belt pretensioner,
airbag sensor assembly or side airbag sensor directly to hot air or flames.

Even in cases of a minor collision where the SRS does not deploy, the steering wheel pad, front passenger airbag
assembly, side airbag assembly, seat belt pretensioner, airbag sensor assembly and side airbag sensor assembly
should be inspected.

Never use SRS parts from another vehicle. When replacing parts, replace them with new parts.

Never disassemble and repair the steering wheel pad, front passenger airbag assembly, side airbag assembly, seat belt
pretensioner, airbag sensor assembly or side airbag sensor assembly in order to reuse it.

If the steering wheel pad, front passenger airbag assembly, side airbag assembly, seat belt pretensioner, airbag sensor
assembly or side airbag sensor assembly has been dropped, or if there are cracks, dents or other defects in the case,
bracket or connector, replace them with new ones.

Use a volt/ohmmeter with high impedance (10 kW/V minimum) for troubleshooting the system's electrical circuits.

Information labels are attached to the periphery of the SRS components. Follow the instructions on the notices.

After work on the SRS is completed, perform the SRS warning light check.

If the vehicle is equipped with a mobile communication system, refer to the precaution in the IN section of the Repair
Manual.

2001 PRIUS (EWD414U)
SRS
C 1
D 11B 215A
AM2 1J 976AM2 AM1ACC
IG1
IG2
ST2
1 2 2 1 2 1 12
SPIRAL
CABLE B 14 B13 B10 B11 A6A5C2C1 10A
SRS ACC FROM POWER SOURCE SYSTEM (
SEE PAGE 50)
2E 4
2B 5
2E 2
B 5B6B23 A7A10 A12 A9C12 C9C7C104 3 2 1 4 3 2 1 3
SIDE AIRBAG
SQUIB RH S 7
SIDE AIRBAG
SQUIB LH S 6
AIRBAG SQUIB
(
FRONT PASSENGER
AIRBAG ASSEMBLY) A20
AIRBAG SQUIB
(
STEERING
WHEEL PAD) A21 IGNITION SW I15
SIDE AIRBAG SENSOR RH S 5
SIDE AIRBAG SENSOR LH S 4
HYBRID VEHICLE
CONTROL ECU H13
FUSIBLE
LINK
BLOCK
NO. 1D F1 2 , F13CAIRBAG SENSOR ASSEMBLYB A17 , A18AC, A19 ABFS
B±G B W±R W±R
B±W B±O
GR
L
P±L
L±W
LG±B
GR ±L
P
L±Y
LG
GR Y±B
Y
Y±R
Y±G
Y±R
Y±G
Y±G
Y±R
BATTERYD+ D± P+ P± SFL+ SFR±SFL± SFR+ IG2 ACC GSW2 VUPL SSL+ SSL± ESL VUPR SSR+ SSR± ESR
GR
2C 2
2G 1
120A MAIN
1
FUSIBLE
LINK BLOCK
NO. 2 F18
1 212 A 2A1C5C6
P15
PRETENSIONER
RH PRETENSIONER
LH P14
Y±B
Y
Y±B
Y
PL+ PL± PR+ PR±
P±L
(
*1)
(
*1)
(
*1)
(
*1)
(
*1)
(
*1)
(
*1)
(
*1) (
*1) (
*1) (
*1) (
*1)

L PART NUMBER OF CONNECTORS
Code Part Name Part NumberCodePart Name Part Number
Note : Not all of the above part numbers of the connector are established for the supply.
2001 PRIUS (EWD414U) L 2
License Plate Light LH90980±11148L 3License Plate Light RH90980±11148
L 4Luggage Compartment Door Unlock SW90980±11212
L 5Luggage Compartment Light90980±11148
L 6Luggage Compartment Light SW90980±11097
M 1Mass Air Flow Meter90980±11317
M 2Motor Generator No.190980±11658
M 3Motor Generator No.290980±11034
M 4Motor Generator No.290980±11143
M 5Multi Display90980±11911
M 6Multi Display90980±11923
M 7Multi Display90980±10799
N 1Noise Filter (Ignition)90980±10843
N 2Navigation ECU90980±11973
N 3Navigation ECU90980±11923
N 4Noise Filter (Rear Window Defogger)90980±11259
O 1Oil Pressure SW90980±11363
P 1Park/Neutral Position SW90980±11535
P 2Parking Brake SW90980±11147
P 3PTC Heater90980±10903
P 4PTC Heater90980±10867
P 5Personal Light90980±11212
P 6Power Window Control SW Front RH
P 7Power Window Control SW Rear LH90980±10797
P 8Power Window Control SW Rear RH
P 9Power Window Master SW90980±11469
P10Power Window Motor Front LH90980±11011
P11Power Window Motor Front RH
P12Power Window Motor Rear LH90980±10860
P13Power Window Motor Rear RH
P14Pretensioner LH90980±11884
P15Pretensioner RH90980±11862
R 1Radiator Fan Motor90980±11237
R 2Radio and Player90980±10996
R 3Radio and Player90980±10997
R 4Radio and Player90980±10903
R 5Remote Control Mirror SW90980±11657
R 6Rear Combination Light LH90980±11011R 7Rear Combination Light RH90980±11011
R 8Rear Speaker LH90980±10935R 9Rear Speaker RH90980±10935
R10Remote Control Mirror LH90980±11587R11Remote Control Mirror RH90980±11587
S 1Steering Shaft Torque Sensor90980±10942
S 2Shift Lock ECU90980±11488
S 3Stop Light SW90980±11118
S 4Side Airbag Sensor LH90980±11857S 5Side Airbag Sensor RH90980±11 857
S 6Side Airbag Squib LH90980±11864S 7Side Airbag Squib RH90980±11864
S 8System Main Relay90980±11529
S 9System Main Relay82675±36050S10System Main Relay82675±36050
S11System Main Relay±S12System Main Relay±
T 1Theft Deterrent Horn90980±10619
T 2Throttle Control Motor90980±11162
T 3Throttle Position Sensor90980±10711
T 4Transponder Key Computer90980±11475
T 5Turn Signal Flasher Relay90980±10799
T 6Tension Reducer Solenoid90980±11918
U 1Unlock Warning SW and Key Interlock
Solenoid90980±10795
V 1Vacuum Sensor (HC Adsorber and Catalyst
System)90980±10845
V 2VSV (EVAP)90980±11156
V 3VSV (HC Adsorber and Catalyst System)90980±11149
V 4Vapor Pressure Sensor90980±11143
V 5VSV (Canister Closed Valve)90980±11156
V 6VSV (Parge Flow Switching Valve)90980±11859
W 1Washer Motor90980±10981
W 2Water Pump Motor (A/C)90980±10887
W 3Water Pump Motor (Inverter)90980±11003
W 4Water Temp. SW90980±11235
W 5Wireless Door Control Receiver90980±11909

2001 PRIUS (EWD414U)
M OVERALL ELECTRICAL WIRING DIAGRAM
1
234
21 PRIUS
2ACC
IG1
ST1
IG2
ST2 AM1
7AM2
1
120A MAIN
1B 1C
1D2H 1
5A AM1
2B 3
ID Co wl s id e
panel LH2K 8
1B 215A
AM2 1J 92C 2
2G 1
A
W±B W± B W± GW
W±R B
WB±G
W±R W± G
I15
IGNITION SW
100 A DC/ DCBATTERYF18
FUSI BLE L I NK
BLOCK NO. 2F11 F12,
FUSIBLE LINK
BL OCK NO. 1BCF13, DSI L TC 5B 12B 19B 6B12C9C7C10C
12
SPI RAL
CA BLE
21
2 1 14 B 13 B 10 B 11 B 9 B 20 B
21 15 B 26 B
B± W
IG2
Y±R
Y
Y± B
A17 A1 8,
AI RBAG SENSOR ASSEMBLYAB
Y± G B± W BR±WW±RBR
F 2
FRONT AIRBAG
S ENSOR RH A21
AI RBAG SQUI B
(
Steering Wheel
Pad)A20
AI RBAG SQUI B
(
Front Passenger
Airbag As sembly)
F 1
FRONT AI RBAG
SENSOR LH±SL +SL ±SR +SR P± P+ D± D+
GR
LG
L±Y
PESR SSR± SSR+ VUPR ACC
3IL1 4IL1 1IL1 2IL1
BR±WW±RBR
GR W P±B
A19 , C
B±O
To Data Link Connector 3
<2±5><2±6>
2 1 6A 5AY±R Y± GS 6
SIDE AIRBAG
SQUIB LHSFL± SFL+
C 2C 1
21
Y± GY±RS 7
S I DE AI RBA G
SQUIB RHSFR+ SFR± 2E 3
C 5C 6
21
Y± BYP15
PRETENSIONER
RHPR± PR+
W± BPL+ PL±
P14
PRETENSIONER
LH
Y
Y± BA
1 21 2A4 3 2 1 123
7A 10A 12A 9A4
GR± L
LG±B
L±W
P±LESL SSL± SSL+ VUPR 3B
LA
B±Y2E 12A 9 2B 4
B±YL
W P± B
2B 5
2E 2B± W
10A ACC
2D 2
2 1
3 5 2C 8
10 A SRS ACC
2E 4
GR± R
P±L
6
B± W
3
P±L
ACC RELAY
S 4
SI DE AI RBAG SENSOR L HS 5
S I DE A I RBA G SE NSOR RH
SRS Power Source
C
B C
A5
B14
A
16 A
LBE+8To Buckle SW LH
< 9±3>
RBE+23 B
LGSW2To Hy brid Vehicle
Con t r ol ECU< 1 ±20 >
11
From Buckle SW RH
<9±3>
G±O
AC
G±O
GR± R BB
GR ±R
J26
JUNCTI ON
CONNECTOR
C10 C1 1,
SRS WARNI NG LI GHT
[COMB. METER]AB J27 J28,
JUNCTION
CONNECTORAB* 1 : w/ Side Air bags
(
*1) (
*1) (
*1) (
*1) (
*1) (
*1) (
*1) (
*1)
(
*1) (
*1) (
*1) (
*1)
28 B
E2
J11
JUNCTI ON
CONNECTOR
Right kick
panel
W±BIHB 27E1W±B
2A 7
2B 6 LLBR

NEW MODEL OUTLINE
MAIN MECHANISM
182CH29
16
4 Features of the 1NZ-FXE engine
1. Highly efficient and high expansion ratio gasoline engine
Adoption of a super fuel-efficient engine developed for use with THS. Its high expansion ratio cycle is achieved by applying the
Atkinson cycle*1 which obtains high thermal efficiency.
2. Reduction in frictional loss
The maximum engine speed is set at 4,500 rpm to reduce frictional resistance, thereby producing a highly efficient low-speed
engine.

An offset crankshaft with 12 mm deviation from the center axis of the cylinder bore is utilized to reduce frictional resistance
of the piston.

Frictional resistance is reduced through the use of low tension valve springs and piston rings.

Lightweight design has been adopted for reciprocating engine parts.
The above measures for reducing frictional loss contribute to improved fuel economy.
3. VVT-i (Variable Valve Timing -intelligent)
The timing of the opening and closing of the intake valves is controlled by the computer according to driving conditions, such
as engine speed and level of acceleration. Thus, smooth intake and exhaust are achieved to greatly improve torque in the low
and medium speed zones. This also contributes to better fuel economy and purification of exhaust gas. Then the VVT-i function
is used to reduce vibration when the engine starts.
4. Compact, lightweight, and low emission
Adoption of an aluminum cylinder block and compact design of parts. And, by positioning the catalytic converter near the engine
for a backwards exhaust layout, we have been able to reduce emissions when the engine is cold started.
*1 : Atkinson Cycle: Proposed by an English engineer named James Atkinson, this thermal cycle enables the compression stroke
and the expansion stroke of the mechanism to be set independently of each other.
Suspension
MacPherson strut type suspension with L-shape
lower arms has been adopted in the front and
torsion beam with toe control link suspension
in the rear. Also, each component part is opti-
mally located and tuned for both excellent con-
trollability and enhanced riding comfort.
EMPS (Electric Motor-assisted Power Steering)
System
Vehicle speed sensing type electric motor-assisted power steering is fitted as standard. Unlike conventional
hydraulic power steering, EMPS does not depend on an engine for its power source, providing a steering feel
in no way inferior to conventional steering when the engine has stopped. Thus it is suitable for the HV system.
Other merits include improved fuel economy through energy conservation, lighter weight, and no need to fill
the power steering fluid.

CHASSIS ± STEERING
182CH62
122
STEERING
DESCRIPTION
A vehicle-speed sensing type EMPS (Electric Motor-assisted Power Steering) has been adopted. The
EMPS uses the EMPS ECU to control a DC motor that is mounted on the steering gear in accordance with
the signals received from various sensors to provide power assist to the steering effort.
A rack and pinion type steering gear and a stepless tilt steering have been adopted.
The steering column has adopted an energy absorbing mechanism that uses energy absorbing plate.

Specifications 
Gear Ratio (Overall)16.4
18.3
No. of Turns Lock to Lock3.99
Rack Stroke mm (in.)149.6 (5.89)

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 

CHASSIS ± STEERING
182CH69
Meter ECU
EMPS ECU
Relay
DC MotorRear Wheel Speed
Sensors and Rotors
Brake ECU Multi-information Display 124
2. Layout of Main Components
3. Function of Main Components
ComponentsFunction
St i
Torque Sensor
Detects the twist of the torsion bar, converts the torque that is applied
to the torsion bar into an electrical signal, and outputs this signal to
the ECU.
Steering
Gear
DC MotorGenerates power assist in accordance with a signal received from the
EMPS ECU.
Reduction
MechanismReduces the rotation of the DC motor and transmits it to the pinion
shaft.
EMPS ECU
Actuates the DC motor mounted on the steering gear for providing
power assist, based on the signals received from various sensors and
the rear wheel speed signal.
Meter ECUOutputs a signal for displaying the PS warning on the center display
in case of a malfunction in the system.
Brake ECURear wheel speed signals are outputted to EMPS ECU.
RelaySupplies power to the DC motor for power assist.
Multi-information DisplayDisplays the PS warning in case of a malfunction in the system.

CHASSIS ± STEERING
182CH70
182CH71
182CH72
Torque
Sensor
Rack and
PinionDC Motor
Reduction Mechanism
Motor
Shaft
Stator
Rotor
Pinion Gear
Motor Shaft
DC Motor
Ring Gear
Pinion Shaft125
4. Construction and Operation of Main Components
Steering Gear
1) General
The steering gear consists of the rack and pin-
ion, DC motor, reduction mechanism, and
torque sensor. The front suspension compo-
nents have been optimized to reduce the load
on the DC motor. Also, the components have
been optimally allocated to ensure ample rack
travel and wheel turning angle, resulting in
excellent cornering performance.
2) DC Motor
The DC motor is mounted on the gear hous-
ing. The DC motor consists of the motor shaft
that is integrated with the hypoid pinion to
transmit the torque that has been generated by
the drive force of DC motor to the pinion
shaft, the rotor and stator.
3) Reduction Mechanism
A reduction mechanism that transmits the
rotation of the motor to the pinion shaft has
been mounted on the steering gear. The reduc-
tion mechanism consists of the ring gear that
is secured to the pinion shaft and the pinion
gear that is integrated with the motor shaft.
The power assist of the motor is transmitted
by the reduction mechanism to the pinion
shaft, which provides power assist to the
steering effort.