2001 TOYOTA PRIUS steering wheel

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.

CHASSIS ± STEERING
182CH73
Contact 1 Resistor 1
Upward
Resistor 2
DownwardContact 2
Contacts Torque
Sensor
Resistor
182CH74
Resistor
Basic
Position
Contact
Straightline 126
4) Torque Sensor
A torque sensor that detects the torque that is input by the steering wheel has been mounted on the pinion
shaft. The torque sensor has been integrated with the pinion shaft, and the pinion shaft's input and output
shafts are linked via the torsion bar. Resistors for the torque sensor are mounted on the input shaft of the
pinion shaft, and contacts for the torque sensor are mounted on the output shaft of the pinion shaft. Oper-
ating the steering wheel causes the torsion bar to twist, creating a displacement between the pinnion
shaft's input and output. Two systems of torque sensors detect this displacement in the form of voltage
changes, which are then output to the EMPS ECU.
i) Straightline Driving
If the vehicle is driven straight and the driv-
er does not turn the steering, torque is not
generated in the pinion shaft's input shaft.
Thus, the torsion bar does not twist, and no
changes in resistance occur in the torque
sensor.

CHASSIS ± STEERING
182CH66
182CH67
Instrument Panel
Reinforcement
Main ShaftInstrument Panel
Reinforcement
Energy Absorbing Plate
Breakaway Bracket
DetachSecondary
Collision
Primary
CollisionContractDeform
After Collision
Before Collision129
ENERGY ABSORBING MECHANISM
The energy absorbing mechanism in the steering column consists of a lower bracket, breakaway bracket, en-
ergy absorbing plate and a contractile main shaft. The steering column is mounted onto the instrument panel
reinforcement via a lower bracket and breakaway bracket which is supported via a capsule and energy absorb-
ing plate. The steering column and the steering gear box are connected with a contractile intermediate shaft.
Operational examples of this mechanism are follows.
When the steering gear box moves during a collision (primary collision), the main shaft and the intermediate
shaft contract, thus reduce the chance that the steering column and the steering wheel protrude into the cabin.
When an impact is transmitted to the steering wheel in a collision (secondary collision), the steering wheel
and the driver airbag help absorb the impact. In addition, the breakaway bracket and the lower bracket sepa-
rate, causing the entire steering column to move forward.
At this time, the energy absorbing plate becomes deformed to help absorb the impact of the secondary collision.

APPENDIX
5
10
15
20
25
30
35
40
45
50
55
60
65
70
Area
Item
Major Dimensions & Vehicle Weights Performance Engine Engine
Chassis
Electrical
192
MAJOR TECHNICAL SPECIFICATIONS
U.S.A. and CanadaBody Type4-Door SedanVehicle GradeÐModel CodeNHW11L-AEEEBANHW11L-AEEEBKLength mm (in.)4305 (169.5)u
OverallWidth mm (in.)1695 (66.7)uOverallHeight mm (in.)1465 (57.6)uWheel Base mm (in.)2550 (100.4)u
TreadFront mm (in.)1475 (58.1)uTreadRear mm (in.)1480 (58.3)u
Effective Head RoomFront mm (in.)985 (38.8)uEffective Head RoomRear mm (in.)942 (37.1)u
Effective Leg RoomFront mm (in.)1047 (41.2)uEffective Leg RoomRear mm (in.)899 (35.4)u
Shoulder RoomFront mm (in.)1342 (52.8)uShoulder RoomRear mm (in.)1325 (52.2)u
OverhangFront mm (in.)815 (32.1)uOverhangRear mm (in.)940 (37.0)uMin. Running Ground Clearance mm (in.)125 (4.9)uAngle of Approach degrees145uAngle of Departure degrees225uFront kg (lb)770 (1700)u
Curb WeightRear kg (lb)485 (1065)uCurb WeightTotal kg (lb)1255 (1765)uFront kg (lb)890 (1965)u
Gross Vehicle WeightRear kg (lb)750 (1650)uGross Vehicle WeightTotal kg (lb)1640 (3615)uFuel Tank Capacity
(US. gal., lmp.gal.)45* (11.9, 9.9)uLuggage Compartment Capacity m3 (cu.ft.)0.39 (137.7)uMax. Speed km/h (mph)160 (99.4)uMax. Cruising Speed km/h (mph)160 (99.4)u
Acceleration0 to 100 km/h sec.12.7uAcceleration0 to 400 m sec.19.0u1st Gear km/h (mph)ÐÐ
Max. Permissible2nd Gear km/h (mph)ÐÐMax. Permissible
Speed3rd Gear km/h (mph)ÐÐp
4th Gear km/h (mph)ÐÐ
Min. Turning RadiusWall to Wall m (ft.)10.2 (33.5)uMin. Turning Radius
(Outside Front)Curb to Curb m (ft.)9.4 (30.8)uEngine Type1NZ-FXEuValve Mechanism16-Valve, DOHCuBore y Stroke mm (in.)75.0 y 84.7 (2.95 y 3.33)uDisplacement cm3 (cu.in.)1497 (91.4)uCompression Ratio13.0uCarburetor TypeSFIuResearch Octane No. RON95uMax. Output (EEC) kW/rpm (HP@rpm)52/4500 (70@4500)uMax. Torque (EEC) N´m/rpm (lb-ft@rpm)111/4200 (82@4200)uBattery Capacity (5HR) Voltage & Amp. Hr.12 ± 28uAlternator Output WattsÐÐStarter Output kWÐÐClutch TypeÐÐTransaxle TypeP111uIn FirstÐÐIn SecondÐÐ
Transmission GearIn ThirdÐÐTransmission Gear
RatioIn FourthÐÐIn FifthÐÐIn ReverseÐÐCounter Gear RatioÐÐDifferential Gear Ratio (Final)3.905u
Brake TypeFrontVentilated DiscuBrake TypeRearL.T. DrumuParking Brake TypeL.T. DrumuBrake Booster Type and Size in.HydraulicuProportioning Valve TypeP-Valveu
Suspension TypeFrontMacPherson StrutuSuspension TypeRearTorsion Beanu
Stabilizer BarFrontSTDuStabilizer BarRearSTDuSteering Gear TypeRack and PinionuSteering Gear Ratio (Overall)16.4~18.3uPower Steering TypeElectric Motoru
*: EPA / CARB ORVR Test conditions

F08459
Marks
IN±22
± INTRODUCTIONFOR ALL OF VEHICLES
22 Author: Date:
2001 PRIUS (RM778U)
(3) Even in cases of a minor collision where the SRS
does not deploy, the steering wheel pad, front pas-
senger airbag assembly, side airbag assembly and
seat belt pretensioner should be inspected (See
page RS±14, RS±28, RS±63 and BO±92).
(4) Never use SRS parts from another vehicle. When
replacing parts, replace them with new parts.
(5) Before repairs, remove the airbag sensor if shocks
are likely to be applied to the sensor during repairs.
(6) Never disassemble and repair the airbag sensor as-
sembly, steering wheel pad, front passenger airbag
assembly, side airbag assembly or seat belt preten-
sioner.
(7) If the airbag sensor assembly, steering wheel pad,
front passenger airbag assembly, side airbag as-
sembly or seat belt pretensioner has been dropped,
or if there are cracks, dents or other defects in the
case, bracket or connector, replace them with new
ones.
(8) Do not directly expose the airbag sensor assembly,
steering wheel pad, front passenger airbag assem-
bly or seat belt pretensioner to hot air or flames.
(9) Use a volt/ohmmeter with high impedance (10 kW/V
minimum) for troubleshooting of the electrical cir-
cuit.
(10) Information labels are attached to the periphery of
the SRS components. Follow the instructions on the
notices.
(11) After work on the supplemental restraint system is
completed, check the SRS warning light (See page
DI±497).
(c) SPIRAL CABLE (in Combination Switch)
The steering wheel must be fitted correctly to the steering
column with the spiral cable at the neutral position, other-
wise cable disconnection and other troubles may result.
Refer to SR±14 of this manual concerning correct steer-
ing wheel installation.

B04764
Example:
Correct Wrong
Z13950
Example:
± INTRODUCTIONFOR ALL OF VEHICLES
IN±23
23 Author: Date:
2001 PRIUS (RM778U)
(d) STEERING WHEEL PAD (with Airbag)
(1) When removing the steering wheel pad or handling
a new steering wheel pad, it should be placed with
the pad top surface facing up.
Storing the pad with its metallic surface facing up-
ward may lead to a serious accident if the airbag de-
ploys for some reason. In addition do not store a
steering wheel pad on top of another one.
(2) Never measure the resistance of the airbag squib.
(This may cause the airbag to deploy, which is very
dangerous.)
(3) Grease should not be applied to the steering wheel
pad and the pad should not be cleaned with deter-
gents of any kind.
(4) Store the steering wheel pad where the ambient
temperature remains below 93°C (200°F), without
high humidity and away from electrical noise.
(5) When using electric welding, first disconnect the air-
bag connector (yellow color and 2 pins) under the
steering column near the combination switch con-
nector before starting work.
(6) When disposing of a vehicle or the steering wheel
pad alone, the airbag should be deployed using an
SST before disposal (See page RS±16).
Carry out the operation in a safe place away from
electrical noise.