Page 769 of 1943

FI7012A11860
P±G A/C Control Assembly
A8 E10522
ACTECM
± DIAGNOSTICSENGINE
DI±171
2001 PRIUS (RM778U)
A/C Cut Control Circuit
CIRCUIT DESCRIPTION
This circuit cuts air conditioning operation during vehicle acceleration in order to increase acceleration per-
formance. During acceleration with the vehicle speed at (AT: 25 km/h (16 mph), MT: 40 km/h (25 mph)) or
less, engine speed at (AT: 1,200 rpm, MT:1,600 rpm) or less and throttle valve opening angle at 60° or more,
the A/C magnet switch is turned OFF for several seconds.
WIRING DIAGRAM
INSPECTION PROCEDURE
TOYOTA hand±held tester:
1 Connect the TOYOTA hand±held tester and check operation of air conditioning
cut control.
PREPARATION:
(a) Connect the TOYOTA hand±held tester to the DLC3.
(b) Turn the ignition switch ON and TOYOTA hand±held tester main switch ON.
(c) Start the engine and air conditioning switch ON.
HINT:
A/C magnet clutch is turned ON.
(d) Select the ACTIVE TEST mode on the TOYOTA hand±held tester.
CHECK:
Check operation of A/C magnet clutch cut when air conditioning cut control is operated by the TOYOTA
hand±held tester.
OK:
A/C magnet clutch is turned OFF.
DI7T8±01
Page 770 of 1943
A14008
START
(±)
(+)ACT
DI±172
± DIAGNOSTICSENGINE
2001 PRIUS (RM778U)
OK Proceed to next circuit inspection shown on
problem symptom table. (See page DI±22)
NG
2 Check for open and short in harness and connector between ECM and A/C am-
plifier. (See page IN±41)
NG Repair or replace harness or connector.
OK
3 Check voltage between terminal ACT of ECM and body ground.
PREPARATION:
(a) Remove the ECM with connector still connected (See
page SF±62).
(b) Start the engine.
CHECK:
Measure voltage between terminal ACT of ECM connector and
body ground when A/C switch is turned to ON and OFF.
OK:
A/C switch conditionVoltage
ON9 ± 14 V
OFFBelow 1.5 V
NG Check and replace A/C amplifier.
OK
Check and replace ECM. (See page IN±41)
Page 771 of 1943
A14008
START
(±)
(+)ACT
± DIAGNOSTICSENGINE
DI±173
2001 PRIUS (RM778U)
OBDII scan tool (excluding TOYOTA hand±held tester):
1 Check voltage between terminal ACT of ECM and body ground.
PREPARATION:
Start the engine.
CHECK:
Measure voltage between terminal ACT of ECM connector and
body ground when A/C switch is turned to ON and OFF.
OK:
A/C switch conditionVoltage
ON9 ± 14 V
OFFBelow 1.5 V
OK Check and repair ECM. (See page IN±41)
NG
2 Check for open and short in harness and connector between ECM and A/C am-
plifier. (See page IN±41)
NG Repair or replace harness or connector.
OK
Check and replace A/C amplifier.
Page 772 of 1943

DI82J±02
Prius Problem Check Sheet
Vehicle
Specifications
Please fill in the blanks within bold frame.Name of DealerPerson in Charge at
HeadquartersPerson in Charge
at Dealer
Model CodeOffice
Vehicle Delivery Date
Frame No.
Unit No. etc.
Option . . . :
( ) Navigation (equipped by ( ) MOP ( ) dealer) ( ) Cold climate specification
( ) others( )Problem Occurrence Date
Service Entry Date NHW11±
. .
. .Registration datemiles
. .
Contents of complaint (Status when and before/after occurring in
the order of events as correct as possible)Characteristics of Customer
Gender
Age
Occupation
Vehicle used before
Main use area
Frequency in use
Others times/day or
week or month
Status of engineOthers
Interview Results
( ) Male ( ) Female
suburbs ( ) %
Others ( ) ( ) %
city area ( ) %
mountain area ( ) %
Driving ConditionRoad Condition
Vehicle Condition
Vehicle Speed
km/h
( ) when starting
( ) when according
( ) When
normal driving
( ) when
decelerating
( ) when braking
( ) when shopping
( ) when parking
( ) when turning
( ) when
ABS actuating
( ) others
( )( ) flat road
( ) up hill ( ) down
hill incline of
° /%
distance
km
( ) dry paved road
( ) wet paved road
( ) rough paved road
( ) unpaved road
( ) snowy/frozen
road
( ) bump/curb
( ) others
( )( ) when starting
( ) right after
starting
( ) until min.
after starting
( ) until min.
after starting
of driving
( ) when shopping
system
( ) while shopping
engine
( ) when starting
engine
( ) when revolving
engineHV Battery
indication
( ) 4/4 ( ) 3/4
( ) 2/4 ( ) 1/4
( ) unidentified
Shift position
(indication)
( ) P ( ) R ( ) N
( ) D ( ) B
( ) when operating
"Weather:
A/C status
( ) no indication
( ) unidentified
( ) A/C ( ) FULL
( ) OFF
( ) unidentifiedWarning light
(MIL)
( ) ON ( ) OFF
( ) PS
( ) main battery
( ) HV!
( ) engine
( ) charge
( ) output
control
( ) brake
( ) ABS
( ) others
( )
Temperature:
°C
Brake operation
( ) brake slowly
( ) Brake suddenly
( ) use two pedals
system
Frequency in
occurrence
( ) always
( ) sometimes
( ) only once
Fuel level
( ) segmentsmphOdometer Reading
mph
°F km
± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
DI±175
2001 PRIUS (RM778U)
CUSTOMER PROBLEM ANALYSIS CHECK
Page 773 of 1943
Verification Results of Warning Light
Engine
HV
INF. code
HV battery
Vehicle Verification Results
( ) ON ( ) OFF
( ) engine ( ) HV
( ) HV battery
( ) output control warning light
( ) brake ( ) ABS ( ) charge ( ) PS
( ) others
( )Verification Results of Diagnostic Code
Brake
PS
Vehicle Inspection Results (Verification items, reason to identify/presume the cause parts, etc.)
Replacement Parts
problem parts: No/Yes (Sending date: . . )Duplication Status
( ) always
( ) sometimes
( ) no reproduction
Confirmation Results
After Repair
( ) Normal
( ) reproduction
( ) others ( )
DI±176
± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
2001 PRIUS (RM778U)
Page 774 of 1943

B04757
DI82K±02
A14091
F12396
DLC3
TOYOTA Hand±held Tester
± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
DI±177
2001 PRIUS (RM778U)
PRE±CHECK
1. PRECAUTION
(a) When distinguishing trouble and replace the defective
part, take necessary preventive measures against an
electric shock (See page IN±4).
(b) Some portions of the wiring harness in the THS vehicle
have circuits to which a high voltage is applied. To prevent
an electrical shock, be sure to observe the following:
(1) Wear insulated gloves during inspection.
(2) Remove a service plug and do not start any repair
operation before 5 minutes have passed. Then,
confirm that the voltage at the output terminals has
dropped down to 12 V or less.
(3) Use insulated tools during inspection.
(4) When disengaging the wiring connectors, hold the
connector bodies to avoid pulling the wires. When
engaging the wiring connectors, be sure to engage
them securely.
(c) Do not leave the tools or parts (bolts, nuts, etc.) inside the
cabin.
(d) Do not carry metallic objects such as mechanical pencils
or scales.
2. DIAGNOSIS SYSTEM
(a) Description
The HV control ECU has a self±diagnosis system
by which malfunction in the computer itself or in
THS components is detected and the Hybrid ve-
hicle warning light in the multi±information display
are lighted up.
To check the Diagnostic Trouble Codes (DTC), con-
nect the hand±held tester to the Data Link Connec-
tor 3 (DLC3) on the vehicle. The TOYOTA hand±
held tester also enables you to erase the DTC and
check freeze frame data and various forms of THS
data.
Page 775 of 1943

A04550
DLC3
912 3 4 56 78
16 15 14 13 12 11 10
DI±178
± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
2001 PRIUS (RM778U)
Freeze frame data:
As the freeze frame data records the driving condi-
tion when a malfunction is detected, when trouble-
shooting, it is useful for determining whether the ve-
hicle was running, braked, stopped or reversed.
(b) Check the DLC3.
The HV control ECU conforms to ISO 14230 for commu-
nication.
The terminal arrangement of the DLC3 complies with
SAEJ1962 and matches the ISO 14230 format.
Terminal No.Connection/Voltage or ResistanceCondition
7Bus Line/Pulse generationDuring transmission
4Chassis Ground e Body Ground/1 W or lessAlways
5Signal Ground e Body Ground/1 W or lessAlways
16Battery Positive e Body Ground/10 ± 15 VAlways
HINT:
If your display shows UNABLE TO CONNECT TO VEHICLE
when you have connected the cable of the TOYOTA hand±held
tester to the DLC3, turned the motor switch ON and operated
the tester, there is a problem in the vehicle or tool.
If communication is normal when the tool is connected to
another vehicle, inspect the DLC3 on the original vehicle.
If communication is still not possible when the tool is con-
nected to another vehicle, the problem is probably in the
tool itself, so consult the Service Department.
3. INSPECT DIAGNOSIS
(a) Check the auxiliary battery.
(1) Measure the voltage of the auxiliary battery.
Voltage: 10 ± 15 V
(2) Inspect the auxiliary battery, fuses, fusible links, wir-
ing harness, connectors and ground.
Page 776 of 1943

A14089
B12009
F12396
DLC3
TOYOTA Hand±held Tester
± DIAGNOSTICSHYBRID VEHICLE CONTROL SYSTEM
DI±179
2001 PRIUS (RM778U)
(b) Check the master warning light.
(1) Turn the ignition switch ON and confirm that the
master warning light comes on.
HINT:
If the master warning light does not come on, suspect a burnt
fuse, burnt bulb, or open in wiring harness.
(2) When the ºREADYº light is ON, the master warning
light should go off.
If the lamp remains on, the diagnosis system has detected a
malfunction in the system or the meassage such as ºWhen you
park your care, make sure you shift to Park P.º and ºThe batter-
ies will not charge if the shifter is Nº appears on the multi±in-
formation display.
Since DTC may be stored even though the lamp is OFF, be sure
to check DTC.
(c) Check the DTC.
(1) Prepare a TOYOTA hand±held tester.
(2) Connect the TOYOTA hand±held tester to the
DLC3.
(3) Turn the ignition switch ON and push the TOYOTA
hand±held tester main switch ON.
(4) Use the TOYOTA hand±held tester to check the
DTC, information code and freeze frame data and
note them down. (For operating instructions, see
the TOYOTA hand±held tester operator's manual).
HINT:
For one DTC, the HV diagnosis system can memorize
more than one information code and freeze frame data
corresponding to them. Therefore, when troubleshooting,
check all of the information codes, record the freeze
frame data and then start inspection according to the pro-
cedures of ºCircuit Inspectionº.
The HV ECU is communicating with each ECU of the en-
gine brake, HV battery and EMPS. So, if a warning is out-
put from the HV control system, check and record DTCs
of all ECUs. (See tables on the following pages.)
(5) See a related page to confirm details of the DTC.