2001 TOYOTA PRIUS O2 sensor

BODY ELECTRICAL ± METER
182BE05
Km / h-MPH Selector Switch
182BE06
Odo Meter
Trip Meter A
Trip Meter B
Odo / Trip Selector / Reset Switch147
2. Construction and Operation
Speedometer

The speedometer is displayed digitally
through the VFD (Vacuum Fluorescent Dis-
play). It can be switched between the km / h
and MPH readings by operating the km / h-
MPH selector switch located in the middle of
the center cluster.

The vehicle speed signal, which originates at
the speed sensor that is installed in the hybrid
transaxle, travels via the HV ECU and ECM
(BEAN) and is received by the meter ECU.
Odo / Trip Meter
Similar to the speedometer, the odo / trip meter is
displayed digitally through the VFD (Vacuum
Fluorescent Display). By operating the odo / trip
selector / reset switch located in the middle of the
center cluster, its display can be switched in the
following sequence: odometer
trip meter A

trip meter B.
While trip meter A or B is displayed, pressing the
odo / trip selector / reset switch 0.8 seconds or
longer causes the driven distance displayed by
the current trip mode to revert to 0.0 mile or 0.0
km.
The trip meter will resume measuring the dis-
tance at the moment the odo / trip selector / reset
switch is released.

BODY ELECTRICAL ± METER
182BE07
Combination Meter
Sender
Gauge
Meter
ECU
Inclination Sensors
Temperature Signal
Sender
Gauge Signal Fuel Injection
Signal
ECM
Body ECU
Sender
Gauge Signal
Fuel TankAmbient
Temperature Sensor
Fuel Sender Gauge
Main Tank Sub Tank Fuel Pump 148
Fuel Gauge
For the purpose of correcting the calculation of the fuel level by the meter ECU, two inclination sensors
that detect the vehicle's longitudinal and latitudinal inclinations have been provided in the meter ECU, and
an ambient temperature sensor has been provided in the fuel tank to detect the temperature in the fuel tank.
The fuel level is calculated by the meter ECU in accordance with the signals of the sender gauge located
in the sub tank that have been received via the body ECU, and the fuel injection signals received from the
ECM. At this time, corrections are made by the signals from the inclination sensors that detect the vehicle's
longitudinal and latitudinal inclinations and the ambient temperature sensor that detects the temperature in
the fuel tank.

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 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.

BODY ELECTRICAL ± AIR CONDITIONING
174BE08
Ex-HI
Blower
Air
Volume
LO
0
Time (a) (b) (c)
Sec.
174BE09
Ex-HI
Blower
Air
Volume
LO
0
Time(a) (b) Sec.169
c. Time-Lagged Air Flow Control
2 types of time-lagged air flow control (in accordance with the temperature detected by the evaporator
temperature sensor) help prevent hot air from being emitted from FACE or BI-LEVEL vent.
i) Evaporator temperature sensor at specified temperature or more
As shown in the diagram on the right, this
control turns OFF the blower motor for
approximately specified time (a) and turns
ON the compressor to cool the air condi-
tioning unit.
After approximately specified time (a)
have elapsed, the blower motor rotates in
the manual LO mode, allowing the cooled
air to be discharged from the vents. Thus,
the discomfort that is associated with the
discharge of warm air is prevented.
Between approximately specified time (b)
to (c), the airflow volume according to the
timelagged airflow control and the airflow
volume of the blower control according to
the calculation of the required outlet air
temperature are compared. The airflow
volume is then regulated at the smaller vol-
ume of the two.
After specified time (c) have elapsed, con-
trol is effected by the blower control ac-
cording to the calculation of the required
outlet air temperature.
ii) Evaporator temperature sensor at specified temperature or less
As shown in the diagram on the right, for
approximately specified time (a), the blow-
er motor rotates in the manual LO mode.
Thereafter, up to approximately specified
time (b), the airflow volume according to
the time-lagged airflow control and the air-
flow volume according to the blower con-
trol of the calculation of the required outlet
air temperature are compared. The airflow
volume is then regulated at the smaller vol-
ume of the two.
After specified time (b) have elapsed, con-
trol is effected based on the blower control
according to the calculation of the required
outlet air temperature.