2001 TOYOTA PRIUS O2 sensor

ENGINE ± 1NZ-FXE ENGINE
182EG25
Engine Load
Full Load Performance
Range 4Range 5
Range 3
Range 2
Range 1Engine Speed
TDC
EXIN
BDCLatest
timing
To retard
side
IN
EX
To advance
side
EX IN71
In proportion to the engine speed, intake air volume, throttle position and water temperature, the ECM cal-
culates an optimal valve timing under each driving condition and control the camshaft timing oil control
valve. In addition, ECM uses signal from the camshaft position sensor and the crankshaft position sensor
to detect the actual valve timing, thus performing feedback control to achieve the target valve timing.

Operation During Various Driving Condition (Conceptual Diagram) 
Operation StateRangeValve TimingObjectiveEffect
During Idling1
182EG26
Eliminating overlap to
reduce blow back to the
intake sideStabilized
idling rpm
Better fuel
economy
At Light Load2
182EG27
Decreasing overlap to
eliminate blow back to
the intake sideEnsured
engine
stability
At Medium
load3
182EG28
Increasing overlap to
increase internal EGR for
pumping loss elimination
Better fuel
economy
Improved
emission
control

ENGINE ± 1NZ-FXE ENGINE
182EG39
Front Airbag
Sensors
(RH and LH)Airbag
Sensor
AssemblyHV
ECUCircuit
Opening
Relay
Fuel Pump
Motor ECM73
7. Fuel Pump Control
A fuel cut control is adopted to stop the fuel pump when the SRS airbag is deployed, thus helping reduce fuel
leakage.
In this system, the airbag deployment signal from the airbag sensor assembly is detected by the HV ECU,
send the signal to ECM, which turns OFF the circuit opening relay.
After the fuel cut control has been activated, turning the ignition switch from OFF to ON cancels the fuel cut
control, thus engine can be restarted.

ENGINE ± 1NZ-FXE ENGINE
182EG31
Accelerator Pedal
Position SensorThrottle Valve
Throttle Position Sensor
Throttle Control
Motor
HV
ECUECM
182EG33 182EG32
Accelerator Pedal
Position Sensor(V)
5.0
4.0
3.0
2.0
1.0
0 10 2030 405060 70 80
125Output Voltage
Accelerator Pedal Depressed AngleVPA2
VPA1 74
8. ETCS-i (Electronic Throttle Control System-intelligent)
General
The ETCS-i, which realizes excellent throttle control in all the operating ranges, has been adopted.
In the conventional throttle body, the throttle valve opening is determined invariably by the amount of
the accelerator pedal effort. In contrast, the ETCS-i used the ECM to calculate the optimal throttle valve
opening that is appropriate for the respective driving condition and uses a throttle control motor to control
the opening.
The ETCS-i controls the ISC (Idle Speed Control) system and the cruise control system.

System Diagram 
Construction
1) Accelerator Pedal Position Sensor
The accelerator pedal position sensor is mounted on the accelerator pedal. To detect the pedal opening
angle, 2 separate systems consisting of main and sub sensors are used, and 2 separate return springs are
used to improve reliability. In the detecting portions, Hall elements have been adopted. Due to the charac-
teristics of the Hall elements, different signals are output depending on whether the pedal is pressed all
the way or is released. To correct these signals, a mechanical device has been provided to detect the cor-
rect pedal opening angle. The sensors of the 2 systems output the same signals.

ENGINE ± 1NZ-FXE ENGINE
150EG39150EG40
Close
Open
VC VTA1 VTA2 E2V
5
0 Close
Output Voltage
Open VTA1 VTA2
Accelerator Pedal Depressed Angle75
2) Throttle Position Sensor
The throttle position sensor is mounted on the throttle body.
The throttle position sensor converts the amount of accelerator pedal effort into two types of electrical
signals with distinct output characteristics. The signals are then input into the ECM.
3) Throttle Control Motor
A DC motor with excellent response and minimal power consumption is used for the throttle control mo-
tor. The ECM performs the duty ratio control of the direction and the amperage of the current that flows
to the throttle control motor in order to regulate the opening angle of the throttle valve.
Operation
The ECM drives the throttle control motor by determining the target throttle valve opening in accordance
with the respective operating condition.
1) Idle Speed Control
The idle speed control is effected entirely by the ETCS-i. The following are the contents of the control:
idle-up control during cold engine operation, intake air volume control to improve the startability of the
engine, and control for when the electrical load changes such as when the air conditioning switch is turned
ON or OFF.
2) Cruise Control
Through the adoption of the ETCS-i, the vehicle speed is now controlled by the throttle control motor,
which controls the throttle valve.

ENGINE ± 1NZ-FXE ENGINE
182EG34
Air CleanerIntake Air Chamber
VSV
(for EVAP)
ECM
Fresh Air Line
Purge Line
EVAP Line
VSV
(for Purge Flow Switching Valve)
Charcoal Canister
Recircle Line
Vapor Pressure
Sensor
VSV (for Canister Closed Valve)77
9. Evaporative Emission Control
General
A vacuum system has been newly adopted to detect leaks in the evaporative emission control system. This
vacuum system detects leaks by forcefully introducing the purge vacuum into the entire system and moni-
toring the changes in the pressure.
In order to detect evaporative emission leaks from the vapor reducing fuel tank, a density method has been
adopted. This system uses an oxygen sensor to measure the HC density in the exhaust gases in order to detect
leaks.
It consists of the following main conponents:

A VSV (for canister closed valve) has been provided between the fresh air line and the fuel tank.

The VSV (for purge flow switching valve) switches the passages from the charcoal canister to the purge
line and from the fuel tank to the purge line.

A vapor pressure sensor has been provided in the fuel tank in order to further ensure the precision of the
vapor pressure sensor.

DTCs (Diagnostic Trouble Codes) have been added. For details on the DTCs (Diagnostic Trouble
Codes), refer to the 2001 Prius Repair Manual (Pub. No.RM778U).

ENGINE ± 1NZ-FXE ENGINE 78
Operation
Initially, the VSV (for canister closed valve) is closed, and the VSV (for EVAP) is open, enabling the VSV
(for purge flow switching valve) to keep the passage between the charcoal canister and the purge line open.
This causes a vacuum to be applied to the purge line, evaporator line, recirculation line, and the line from
the charcoal canister to the fuel tank.
Next, the VSV (for EVAP) is closed in order to maintain a vacuum from the VSV (for EVAP) to the inside
of the fuel tank. Then, any subsequent changes in the pressure are monitored by the vapor pressure sensor
in order to check for evaporative emission leaks.
Next, the VSV (for canister closed valve) and the VSV (for EVAP) open, enabling the VSV (for purge flow
switching valve) to keep the passage between the fuel tank and the purge line open. Then, the air in the fuel
tank is drawn in by the vacuum of the intake chamber, and the density of HC in the exhaust gases is measured
by the oxygen sensor to detect any leaks.
If a leak is detected, the malfunction indicator lamp (MIL) illuminates to inform the driver. Also, the diag-
nostic trouble code (DTC) can be accessed through the use of a hand-held tester.
For details on the DTCs, refer to the 2001 Prius Repair Manual (Pub. No.RM778U).
10. HV Immobiliser System
The HV immobiliser system has been designed to prevent the vehicle from being stolen. This system uses
a HV ECU 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 HV ECU prohibit fuel delivery, ignition, and starting the HD system effective-
ly disabling the engine.
For details see page 184 in the HV Immobiliser System section.
11. Diagnosis System
The diagnostic trouble codes can be output via DLC3 to an OBD-II scan tool or a hand-held tester. For details,
refer to the 2001 Prius Repair Manual (Pub. No.RM778U).

THS (TOYOTA HYBRID SYSTEM)
182TH19
EngineECMHV ECU
Shift Position Sensor
Brake ECU
HV Battery
Accelerator Pedal Position Sensor
Hybrid Transaxle Inverter with Converter
Battery ECU
SMR (System Main Relay)
Service Plug23

FEATURES OF THS
This system controls the following modes in order to achieve the most efficient operations to match the driv-
ing conditions:
1. Supply of electrical power from the HV battery to MG2 provides force to drive the wheels
2. While the tires are driven by the engine via the planetary gears, MG1 is driven via the planetary gears to
supply electricity to MG2 to drive the wheels
3. When the vehicle is decelerating, kinetic energy from the wheels is recovered and converted into electrical
energy and used to recharge the HV battery by means of MG2.
The HV ECU switches between these modes (1, 2, 1 + 2, or 3) according to the driving conditions. However,
when the SOC of the HV battery is low, the HV battery is charged by the engine by turning MG1.
As a result, it achieves far greater the fuel economy compared to conventional gasoline engine vehicles, at
a reduced level of exhaust gas emissions. Furthermore, this revolutionary powertrain has eliminated the
constraints that are associated with electric vehicles (such as their short cruising range or their reliance on
external recharging units).

LAYOUT OF MAIN COMPONENTS

THS (TOYOTA HYBRID SYSTEM) 24

MAIN FUNCTIONS OF COMPONENTS
MG1Generates high-voltage electricity by being powered primarily by the engine.
Also functions as a starter to start the engine.
Hybrid
Trans-
axle
MG2
Primarily provide additional power to the engine in order to increase the
overall drive force. During braking, or when the accelerator pedal is not
depressed, it generates electricity to recharge the HV battery (Regenerative
brake system).
Planetary
Gear UnitDistributes the engine's drive force as appropriate to directly drive the vehicle
as well as the generator.
HV Battery
Supplies electric power to the MG2 during start-off, acceleration, and uphill
driving; recharged during braking or when the accelerator pedal is not
depressed.
InverterA device that converts the high-voltage DC (HV battery) into AC (MG1 and
MG2) and vice versa (Converts AC into DC).
Converter
Drops the high-voltage direct current (DC 273.6 V) into DC12 V in order to
supply electricity to body electrical components, as well as to recharge the
auxiliary battery (12 V).
HV (Hybrid Vehicle
Control) ECU
Information from each sensor as well as from the ECU (ECM, Battery ECU,
ABS ECU) is received, and based on this the required torque and output power
is calculated.
The HV ECU sends the calculated result to the actuators and controllers.
ECMSends a throttle open command to the electronically-controlled throttle in
accordance with the engine output request factor received from the HV ECU.
Battery ECUMonitors the charging condition of the HV battery.
Brake ECU
Controls the regenerative brake that is effected by the MG2 and the hydraulic
brake so that the total braking force equals that of a conventional vehicle that
is equipped only with hydraulic brakes.
Also, the brake ECU performs the ABS control conventionally.
Accelerator PedalConverts the accelerator angle into an electrical signal and outputs it to the HVAccelerator Pedal
Position Sensor
Converts the accelerator angle into an electrical signal and outputs it to the HV
ECU.
Shift Position SensorConverts the shift lever position into an electrical signal and outputs it to the
HV ECU.
SMR (System Main
Relay)Connects and disconnects the high-voltage power circuit through the use of
a signal from the HV ECU.
Service plugShuts off the high-voltage circuit of the HV battery when this plug is removed
for vehicle inspection or maintenance.