2001 TOYOTA PRIUS air condition

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.

BODY ELECTRICAL ± AIR CONDITIONING
182BE51
Hi
Lo Blower
Air
Volume
Small Large
Amount of Sunligt
182BE28182BE29
1
0
Small Large
Vehicle Speed Fresh Air
Recirculation
182BE52
Outlet Air
Half
Inlet Air
Low High
TAO (Temperature Air Outlet) 170
d. Sunlight Air Flow Control
Controls the blower speed in accordance
with the intensity of the sunlight when the air
outlet mode is at FACE or BI-LEVEL. The
blower low speed can be adjusted up to 4
steps, in response to the sunlight signal re-
ceived from the solar sensor.
2-Way Flow Mode Control
At the time of selecting FRESH mode, air conditioning ECU will judge it as 2-way flow mode when the
blower outlet is selected to FOOT or FOOT / DEF, the tentative air mix damper opening angle is above the
specified valve (MAX HOT), and either the blower volume is more than the specified volume or the vehicle
speed is less than the specified speed.
Half Inlet Air Mode Control
At the time of selecting FRESH mode, air condi-
tioning ECU will judge it as half inlet air mode
when the blower outlet mode is selected to FACE
or BI-LEVEL and TAO (Temperature Air Out-
let) is more than the specified temperature, and
operates both outlet air introduction and inlet air
circulation at the same time.

BODY ELECTRICAL ± AIR CONDITIONING
182BE31
Tentative Damper Opening Angle
(During 2-Way Flow Mode)
Damper
Opening
Recirculation /
Fresh Air
SwitchingFresh
Air
2-Way
Flow
MAX HOT
182BE33
A / C SwitchMAX
Switch171
Air Inlet Control System
1) Manual Control
Drives the air inlet servomotor according to
the operation of the air inlet control switch and
fixes the dampers in the FRESH or RECIRC
position.
The 2-way flow mode control switches the re-
circulation / fresh-air function in accordance
with the opening of the air mix damper, calcu-
lates the target opening of the damper, and ro-
tates the servomotor.
2) Battery ECU Forced Fresh Air Mode
When the air conditioning ECU receives the forced fresh air mode signal from the battery ECU via the
HV ECU and the ECM, the damper forcefully switches to the FRESH mode.
3) DEF, FOOT / DEF Mode Control
When the mode switching switch is switched to FOOT / DEF mode from DEF mode or other than
FOOT / DEF mode, air conditioning ECU switches to FRESH mode forcibly.
Also, when the mode switching switch is switched to DEF mode from other than DEF mode, air condi-
tioning ECU turns MAX mode ON and switched to FRESH mode forcibly.
Compressor Control System
1) OFF Control
Turns OFF the magnetic clutch of the compressor when the conditions for turning the blower motor OFF
during warm-up control have been met.
2) Compressor Lock Judgment
When the magnetic clutch is ON, if the air
conditioning ECU judges that the compressor
has been locked, it turns OFF the magnetic
clutch relay and flashes the indicator lamp in
the A / C or MAX switch. The conditions in
which the ECU judges the compressor to have
locked are when a slippage rate of 80% or
more has been continued for 3 seconds or
more.

BODY ELECTRICAL ± AIR CONDITIONING 172
3) Refrigerant Pressure Malfunction Detection
By monitoring the pressure switch signal, this system can judge the refrigerant pressure to be abnormal,
and turns off the compressor magnetic clutch relay, if the pressure switch remains off.
4) MAX Switch ON Control
a. General
In case of usual air conditioning operation, the air conditioning system shows superior control on cool-
ing performance and fuel efficiency by combining the engine ON / OFF control by the hybrid control
and the air conditioning ON / OFF control.
In this MAX switch ON control, it controls by attaching greater importance to cooling performance of
the air conditioning.

BODY ELECTRICAL ± ACCESSORIES
182BE44
SRS
Warning LightInflator and Bag
for Front Passenger
Front Airbag
Sensor (RH)
Side Airbag
Assembly (RH)
Seat Belt
Pretensioner (RH)
Side Airbag
Sensor (RH) Airbag Sensor
Assembly Seat Belt
Pretensioner (LH) Side Airbag
Sensor (LH) Side Airbag
Assembly (LH)Front Airbag
Sensor (LH)Inflator and Bag
for Driver
182BE45
CollisionImpact
Front Airbag Sensors
Airbag Sensor
Assembly
 Inflator
 (For Driver and Front Passenger)
 Seat Belt Pretensioner
 (LH and RH)
Inflator
(For Right Side or Left Side)
CollisionImpactSide
Airbag
Sensor 188
SRS AIRBAG AND SRS SIDE AIRBAG
The SRS (Supplemental Restraint System) airbags are provided for the driver and front passenger. The
SRS airbags have been designed to help reducing the shocks to the heads and chests of the driver and front
passenger in the event of a frontal impact collision as supplements to the seat belts.
This system is a 3-sensor type airbag system to detect the impact during a front collision using the airbag
sensor assemblies and front airbag sensor, and to make the airbag system and seat belt pretensioner operate
as well.
Also, the function of the ECU to memorize the seat belt wearing condition while inflating the airbag is
added.
The SRS side airbags are provided for the driver and front passenger as an option. The SRS side airbags
have been designed to help reducing the impact energy that is transmitted to the driver and front passenger
in the event of a side collision.
The driver side and the front passenger side are each provided with one sensor.
A fuel cut control has been adopted to stop the fuel pump when the SRS airbag is deployed, thus helping
reduce fuel leakage.

System Diagram 

± INTRODUCTIONFOR ALL OF VEHICLES
IN±15
15 Author: Date:
2001 PRIUS (RM778U)

When the master warning light is lit during operation
in the inspection mode, deactivate the inspection
mode and inspect the diagnosed area.
HINT:
When continuous operation of the engine is required for such
as an exhaust leakage inspection, it is advisable as an easier
way to turn ON the FULL switch of the air conditioner.
5. SPECIAL NOTES FOR VEHICLE INSPECTION
(a) Vehicle conditions
(1) Before activating the service mode, turn the air con-
ditioner off, start the engine with the shift lever at P
position, and check that the engine stops within
several seconds after starting. (Engine warm up
check)
(2) Activate the service mode and inspect the vehicle.
The shift position for each test is as follows:
Test itemShift lever position
1. Vehicle straight traveling test (side
slip inspection)D
2. Braking force testN
3. Speedometer testD
4. Exhaust gas test (idling)P
5. Headlight testP
(3) Reset the service mode immediately after comple-
tion of inspection.
NOTICE:
Traveling on a road without resetting the service mode may
damage the transaxle.
(b) Special notes for speedometer test
NOTICE:
Rapid starting or quick acceleration/deceleration based on
the speedometer tester without load setting may damage
the transaxle.
(1) Depress the accelerator pedal slowly and gradually
accelerate at the time of measurement.
(2) After the measurement, use the brake to decelerate
gradually and stop.
(c) Special note for using the chassis dynamometer
Always set an appropriate load before starting the test.
NOTICE:
Rapid starting or quick acceleration/deceleration with in-
sufficient load may damage the transaxle.

IN05Y±22
± INTRODUCTIONHOW TO TROUBLESHOOT ECU CONTROLLED
SYSTEMSIN±29
29 Author: Date:
2001 PRIUS (RM778U)
HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
GENERAL INFORMATION
A large number of ECU controlled systems are used in the PRIUS. In general, the ECU controlled system
is considered to be a very intricate system requiring a high level of technical knowledge and expert skill to
troubleshoot. However, the fact is that if you proceed to inspect the circuits one by one, troubleshooting of
these systems is not complex. If you have adequate understanding of the system and a basic knowledge
of electricity, accurate diagnosis and necessary repair can be performed to locate and fix the problem. This
manual is designed through emphasis of the above standpoint to help service technicians perform accurate
and effective troubleshooting, and is compiled for the following major ECU controlled systems:
The troubleshooting procedure and how to make use of it are described on the following pages.
SystemPage
6. EngineDI±1
7. Hybrid Vehicle Control SystemDI±174
8. HV Battery Control SystemDI±312
9. Anti±Lock Brake System With EBD & RBSDI±351
10.Electric Motor Power SteeringDI±452
11. Supplemental Restraint SystemDI±495
12.Cruise Control SystemDI±640
13.Combination Meter SystemDI±662
14.Body Control SystemDI±678
15.Driver Door Control SystemDI±730
16.Multiplex Communication SystemDI±750
17.Navigation SystemDI±789
18.Air Conditioning SystemDI±864
FOR USING OBD II SCAN TOOL OR TOYOTA HAND±HELD TESTER

Before using the scan tool or tester, the scan tool's instruction book or tester's operator manual should
be read thoroughly.

If the scan tool or tester cannot communicate with ECU controlled systems when you have connected
the cable of the scan tool or tester to DLC3, turned the ignition switch ON and operated the scan tool,
there is a problem on the vehicle side or tool side.
(1) If communication is normal when the tool is connected to another vehicle, inspect the diagnosis
data link line (Bus
line) or ECU power circuit of the vehicle.
(2) If communication is still not possible when the tool is connected to another vehicle, the problem
is probably in the tool itself, so perform the Self Test procedures outline in the Tester Operator's
Manual.