coolant temperature TOYOTA PRIUS 2001 Service Repair Manual

ENGINE ± 1NZ-FXE ENGINE
182EG10
171EG17
From Heater
To Heater
To Radiator
From Radiator
Water Pump
Cylinder Head
Heater Core
Throttle Body
Radiator Cylinder Block Bypass
Passage
Water Pump
Thermostat53
COOLING SYSTEM
1. General

The cooling system is a pressurized, forced-circulation type.

A thermostat with a bypass valve is located on the water inlet housing to maintain suitable temperature
distribution in the cooling system.

The flow of the engine coolant makes a U-turn in the cylinder block to ensure a smooth flow of the engine
coolant.

The radiator for the engine and the A / C condenser have been integrated to minimize the space they occupy
in the engine compartment.

ENGINE ± 1NZ-FXE ENGINE
182EG12
A ± A Cross Section Throttle Control Motor
AA
Throttle Position SensorReturn Spring
Opener Spring
182EG13
Vacuum Port55
INTAKE AND EXHAUST SYSTEM
1. Throttle Body

The adoption of the ETCS-i has realized excellent throttle control.

The ISC system and cruise control system are controlled comprehensively by the ETCS-i.

The ETCS-i, which drives the throttle valve through a DC motor that is controlled by the ECM, thus doing
away with a throttle link to connect the accelerator pedal to the throttle valve, has been adopted.

The throttle control motor is provided with a return spring that closes the throttle valve.

An opener spring is provided on the throttle position sensor side. This spring opens the throttle valve slight-
ly when the engine is stopped to prevent the throttle valve from sticking and to improve the engine's restart-
ability.

A warm coolant passage is provided below the throttle body to prevent the throttle valve from freezing
during cold temperatures.
2. Intake Manifold

Because it is not necessary to improve the in-
take air efficiency through inertial intake due to
the adoption of the Atkinson cycle, the length
of the intake pipe of the intake manifold has
been shortened, and furthermore, the intake
pipes for cylinders #1 and #2, as well as for #3
and #4, have been integrated midstream to
achieve a large-scale weight reduction.
In addition, the throttle body has been oriented
downflow in the center of the surge tank to
achieve a uniform intake air distribution.

A vacuum port has been provided for the Toyo-
ta HC adsorber and catalyst system.

ENGINE ± 1NZ-FXE ENGINE62
ENGINE CONTROL SYSTEM
1. General
The engine control system for the 1NZ-FXE engine has following system.
System
Outline
SFI
Sequential Multiport
Fuel InjectionAn L-type SFI system directly detects the intake air volume with a hot-wire
type mass air flow meter.
ESA
Electronic Spark
AdvanceIgnition timing is determined by the ECM based on signals from various
sensors. The ECM corrects ignition timing in response to engine knocking.
VVT-i
Variable Valve
Timing-intelligentControls the intake camshaft to an optimal valve timing in accordance with
the engine condition.
ETCS-i
Electronic
Throttle Control
System-intelligentOptimally controls the throttle valve opening in accordance with the ECM,
and the conditions of the engine and the vehicle, and comprehensively
controls the ISC and cruise control system.
Fuel Pump Control
Fuel pump operation is controlled by signal from the ECM.

To stop the fuel pump during operation of the SRS airbag.
Oxygen Sensor Heater
ControlMaintains the temperature of the oxygen sensors at an appropriate level to
increase accuracy of detection of the oxygen concentration in the exhaust gas.
Evaporative Emission
Control

The ECM controls the purge flow of evaporative emissions (HC) in the
charcoal canister in accordance with engine conditions.

Using 3 VSVs and a vapor pressure sensor, the ECM detects any
evaporative emission leakage occurring between the fuel tank and the
charcoal canister, and vapor reducing fuel tank through the changes in the
tank pressure. For details, see page 79.
Toyota HCAC System
The ECM controls the VSV (for Toyota HCAC System) to improve the clean
emission performance of the exhaust gas when the temperature of the TWC
is low. For details, see page 58.
Air Conditioning
Cut-Off ControlBy turning the air conditioning compressor OFF in accordance with the
engine condition, drivability is maintained.
Cooling Fan ControlRadiator cooling fan operation is controlled by signals from ECM based on
the engine coolant temperature sensor signal (THW).
HV Immobiliser
Prohibits fuel delivery, ignition, and starting the HV system if an attempt is
made to start the HV system with an invalid ignition key. For details, see page
80.
DiagnosisWhen the ECM detects a malfunction, the ECM diagnoses and memorizes
the failed section.
Fail-SafeWhen the ECM detects a malfunction, the ECM stops or controls the engine
according to the data already stored in memory.

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.

BODY ELECTRICAL ± AIR CONDITIONING
182BE17
PTC Heaters
182BE18
ALT AM1Ignition
Switch
HTR
MAIN
PS
HTR1PTC
HTR1PTC
HTR2
Battery
Heater Core
Integrated
PTC HeaterPTC Heaters
IG
HTR0
Air
Conditioning
ECU
HTR2
GNDMPX
IDH
Switch Signals from
Heater Control Panel
ECM
Body
ECU
Converter
Ambient
Temperature Sensor
Engine Coolant
Temperature Sensor
156
PTC heaters have been provided in the air
duct at the footwell outlet in front of the air
conditioning unit. However, air condition-
ing without the PTC heaters is offered as an
option on the U.S.A. models.
This PTC heater, which is a honeycomb-
shaped PTC thermistor, directly warms the
air that flows in the duct.

Wiring Diagram 

BODY ELECTRICAL ± AIR CONDITIONING157
2) Operation
a. Heater Core Integrated PTC Heater Model
The heater turns ON when all the conditions listed below have been met.
i) Outlet is in the DEF mode:
Coolant temperature is below the specified value.
Ambient temperature is below the specified value.
Converter's PTC heater prohibition signal is OFF.
ii) Outlet is in the FOOT or FOOT / DEF mode:
Coolant temperature is below the specified value.
Tentative air mix damper opening angle is above the specified value. (MAX HOT)
Converter's PTC heater prohibition signal is OFF.
b. Heater Core Integrated PTC Heater and PTC Heater Model
In the case of the heater core integrated PTC heater and PTC heater model, the conditions under which
the heater core integrated PTC heater operates are the same as those for the heater core integrated PTC
heater model described above. Furthermore, in the heater core integrated PTC heater and PTC heater
model, the PTC heater turns ON when all the conditions listed below have been met.
Outlet is in the FOOT or FOOT / DEF mode.
Blower switch in the ON state.
Coolant temperature is below the specified value.
Tentative air mix damper opening angle is above the specified value. (MAX HOT)
Converter's PTC heater prohibition signal is OFF.

BODY ELECTRICAL ± AIR CONDITIONING
182BE22
Air
Conditioning
ECUBEAN
ECM
Room Temper-
ature SensorEvaporator Tem-
perature SensorSolar SensorAmbient Tem-
perature SensorEngien Coolant
Temperature Sensor
182BE23
Ambient Temperature Sensor165
6. Air Conditioning ECU
General
An automatic control type air conditioning has been adopted. This system uses an air conditioning ECU
to perform the calculation of the required outlet air temperature control, temperature control, blower con-
trol, air inlet control, air outlet control, and compressor control.
The information that is necessary for effecting the controls are the signals from the room temperature
sensor, evaporator temperature sensor, and solar sensor that are directly transmitted to the air condition-
ing ECU, and the signals from the ambient temperature sensor and the engine coolant temperature sensor
that are transmitted via the ECM. These signals are calculated by the air conditioning ECU to effect the
proper control.

System Diagram 
Sensors
1) Ambient Temperature Sensor
The ambient temperature sensor has been pro-
vided on the left, in front of the condenser.
The signals from this sensor are transmitted to
the air conditioning ECU via the ECM.

BODY ELECTRICAL ± AIR CONDITIONING
182BE24Room Temperature
Sensor
182BE25
Evaporator Temperature
Sensor
182BE26
Solar Sensor
182BE27
Engine Coolant
Temperature Sensor 166
2) Room Temperature Sensor
The room temperature sensor has been pro-
vided inside the instrument finish lower panel.
The signals from this sensor are directly trans-
mitted to the air conditioning ECU.
3) Evaporator Temperature Sensor
The evaporator temperature sensor has been
provided behind the evaporator in the air
conditioning unit.
The signals from this sensor are directly trans-
mitted to the air conditioning ECU.
4) Solar Sensor
The solar sensor has been provided on top of
the instrument panel.
The signals from this sensor are directly trans-
mitted to the air conditioning ECU.
5) Engine Coolant Temperature Sensor
The water temperature sensor has been pro-
vided on the water outlet area on the left side
of the engine.
The signals from this sensor are transmitted to
the air conditioning ECU via the ECM.

BODY ELECTRICAL ± AIR CONDITIONING
182BE50
Large
Target
Damper
Opening
Angle
Small
Large Small
Tentative Damper Opening Angle167
Calculation of Required Outlet Air Temperature (TAO: Temperature Air Outlet)
After receiving the signals from the sensors and the temperature control switch setting, the air conditioning
ECU uses the formula shown below to calculate the required outlet air temperature, to regulate the servomo-
tors and blower motor. This is an outlet air temperature that is required in maintaining the set temperature
in a stable manner.
TAO=KSETx TSET±Kr x TR±KAMx TAMdisp±KsxTS+C±TCTA O = KSET x TSET ± Kr x TR ± KAM x TAMdisp ± Ks x TS + C ± TC
KSET= Setting Temperature Coefficient TSET = Setting Temperature
Kr = Room Air Temperature Coefficient TR = Room Air TemperatureKr= Room Air Temperature CoefficientTR= Room Air Temperature
K
AM= Ambient Air Temperature Coefficient TAMdisp = Ambient Air TemperatureAMppp
Ks = Solar Radiation Coefficient TS = Solar Radiation
C = Correct Constant TC = Compressor ON / OFF CorrectC= Correct ConstantTC= Compressor ON / OFF Correct
= Constant
Temperature Control System
1) Air Mix Damper Control
In response to the temperature control switch setting, the required ambient temperature, evaporator tem-
perature sensor, and engine coolant temperature sensor compensations are used by the air mix damper
control to calculate a tentative damper opening angle, through an arithmetic circuit in the air mix damper,
to arrive at a target damper opening angle.

Calculating the Target Damper Opening 

BODY ELECTRICAL ± AIR CONDITIONING
174BE06
Ex-HI
Blower
Air
Volume
LO
Low
Required Outlet
Air TemperatureHigh[C]
174BE07
HI
Calculated
Air Volume
LO
OFF[C]
Coolant Temperature (a) (b) (c) 168
Blower Control System
1) Blower Motor Startup Control
When the blower motor is started up, the blower voltage in the auto mode (low speed) is output to the
blower controller for 3 seconds. This is designed to protect the blower controller from a sudden startup
current surge.
2) Manual Control
Sets the blower speed according to operation of the blower switch.
3) Automatic Control
a. Stepless Air Volume Control
As shown on the right, when the AUTO
switch on the heater control panel is pushed,
the air conditioning ECU automatically reg-
ulates the voltage to the blower controller, in
accordance with the required outlet air tem-
perature, to deliver stepless air volume.
b. Warm-Up Control
When the coolant temperature detected by the engine coolant temperature sensor is below a predeter-
mined level and the air outlet is in the FOOT or BI-LEVEL mode, the blower does not operate. When
the coolant temperature reaches specified temperature (b), the blower motor operates at low speed.
When the coolant temperature is between specified temperature (b) to (c), the air flow calculation using
the engine coolant temperature sensor signal, and, the air flow calculation using the required outlet air
temperature are compared, and the lesser of the two is automatically selected as the air flow to be used.
When the coolant temperature reaches specified temperature (c) or more, the blower motor runs at high
speed. Moreover, when the coolant temperature is under specified temperature (a), and the warm-up
control is effected (blower motor off), the air outlet is switched to the DEF mode. Later, when the blower
motor turns on, the air outlet changes from the DEF mode to the FOOT or BI-LEVEL mode.