2001 TOYOTA PRIUS O2 sensor

Resistance of photodiode
Strength of solar radiationWeak Strong
High
Low
I18378
A/C Amplifier
A12
A/C Solar
Sensor
A9A9
TSS5TS
5 6
1
2W
W
± DIAGNOSTICSAIR CONDITIONING SYSTEM
DI±893
2001 PRIUS (RM778U)
DTC 21 Solar Sensor Circuit
CIRCUIT DESCRIPTION
A photo diode in the solar sensor detects solar radiation and
sends signals to the A/C amplifier.
DTC No.Detection ItemTrouble Area
Open or short in solar sensor circuit
Solar sensor
21
Open or short in solar sensor circuit.
(Please note that display of DTC 21 is not abnormal when the
Harness or connector between solar sensor and A/C amplifi-
er(y
sensor is not receiving solar radiation.)er.

A/C amplifier.
WIRING DIAGRAM
DI7S9±01

I18163
ON
(±)TS
S5TS
(+)
DI±894
± DIAGNOSTICSAIR CONDITIONING SYSTEM
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check voltage between terminals S5TS and TS of A/C amplifier connector.
PREPARATION:
(a) Remove center cluster module control with connectors
still connected.
(b) Turn ignition switch ON.
CHECK:
Measure voltage between terminals S5TS and TS of A/C ampli-
fier connector when the solar sensor is subjected to an electric
light, and when the sensor is covered by a cloth.
OK:
ConditionVoltage
Sensor subjected to electric lightBelow 4.0 V
Sensor covered by a cloth4.0 ± 4.5 V
HINT:
As the inspection light is gradually moved away from the sen-
sor, the voltage increases.
NG Go to step 2.
NG
Proceed to next circuit inspection shown on problem symptoms table (See page DI±874). Howev-
er, if DTC 21 is displayed, check and replace A/C amplifier.

I00325
± DIAGNOSTICSAIR CONDITIONING SYSTEM
DI±895
2001 PRIUS (RM778U)
2 Check solar sensor.
PREPARATION:
Remove solar sensor (See page AC±59).
CHECK:
(a) Cover the sensor by a cloth.
(b) Measure resistance between terminals 1 and 2 of solar
sensor connector.
HINT:
Connect positive (+) lead of ohmmeter to terminal 2 and nega-
tive (±) lead to terminal 1 of the solar sensor.
OK:
Resistance : 8W (No continuity)
PREPARATION:
Remove the cloth from the solar sensor and subject the sensor
to electric light.
CHECK:
Measure resistance.
OK:
Resistance : Below 10 kW (Continuity)
HINT:
As the electric light is moved gradually away from the sensor,
the resistance increases.
NG Replace solar sensor.
OK
3 Check harness and connector between A/C amplifier and solar sensor
(See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace A/C amplifier.

I18379
Compressor
Lock SensorA/C Amplifier
4
29
A8LOCK W±L
18
A8SG LOCK IE14
BR±WW±L
W±LIK14
IK15
BR±W BR±W
IE15 DI±896
± DIAGNOSTICSAIR CONDITIONING SYSTEM
2001 PRIUS (RM778U)
DTC 22 Compressor Lock Sensor Circuit
CIRCUIT DESCRIPTION
This sensor sends 1 pulse par engine revolution to the A/C amplifier. If the number ratio of the compressor
speed divided by the engine speed is smaller than a predetermined value, the A/C amplifier turns the com-
pressor off. And, the indicator flashes at about 1 sec. intervals.
DTC No.Detection ItemTrouble Area
All diti b l d t t d f 3
CompressorAll conditions below are detected for 3 secs. or more.
( ) E i d 450

Com ressor

Compressor drive belt
22(a) Engine speed : 450 rpm or more.
(b) Ratio between engine and compressor speed deviates

Com ressor drive belt

Compressor lock sensor22(b) Ratio between engine and compressor speed deviates
20 % or more in comparison to normal operation

Com ressor lock sensor

Harness or connector between compressor and A/C amplifier 20 % or more in comparison to normal operation.Harness or connector between com ressor and A/C am lifier

A/C amplifier
WIRING DIAGRAM
DI7SA±01

I18005
2
4
N02774
0.2 V/Din.0 V
20 msec/Division (Idling)LCK1 LOCK signal waveform
± DIAGNOSTICSAIR CONDITIONING SYSTEM
DI±897
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check compressor.
PREPARATION:
(a) Check compressor drive belt tension (See page AC±15).
(b) Check if the compressor does not lock during operation with engine started and blower switch and A/C
switch ON.
NG Adjust drive belt tension or repair compressor.
OK
2 Check compressor lock sensor.
PREPARATION:
Disconnect compressor lock sensor connector.
CHECK:
Measure resistance between terminals 2 and 4 of compressor
lock sensor connector.
OK:
Resistance : at 20 °C (68 °F) : 65 ± 125 W
Reference : Inspection using oscilloscope
During cranking or idling, measure voltage between terminals
LOCK and SGLOCK of A/C amplifier.
HINT:
The correct waveform appears as shown in the illustration on
the left.
NG Replace compressor.
OK

I08340
J1
J/CL±Y
A3
A/C Dual Pressure
SwitchA/C amplifier
W±B
IE1
A811
PSW
4
ED 115
A W±B
± DIAGNOSTICSAIR CONDITIONING SYSTEM
DI±899
2001 PRIUS (RM778U)
DTC 23 Pressure Switch Circuit
CIRCUIT DESCRIPTION
This pressure switch sends the appropriate signals to the A/C amplifier when the A/C refrigerant pressure
drops too low or rises too high. When the A/C amplifier receives these signals, if outputs signals via the A/C
amplifier to switch off the compressor relay and turns the magnetic clutch off.
DTC No.Detection ItemTrouble Area

Open inpressure sensor circuit
Pressure switch
23

Open in pressure sensor circuit.

Abnormal refri
gerant pressure.
Pressure switch

Harness or connector between pressure switch and A/C am-
lifi23
Abnormal refrigerant ressure.
below 196 kPa (2.0 kgf/cm2. 28 psi)2
plifier


Refrigerantpipe lineover 3,140 kPa (32.0 kgf/cm2. 455 psi)
Refrigerant pipe line

A/C amplifier
WIRING DIAGRAM

DI7SB±01

4(V)
1
0
100%
TPI terminal voltage
Damper opening angle
I18402
A16
Air Mix Control
Servomotor
A/C Amplifier
6
S5TP
SGTP
TP 17
15
A916 A9A9
II1
3
B
V 21W
W±R
BR±WW 8
II1
W 7
II1 Y±R DI±902
± DIAGNOSTICSAIR CONDITIONING SYSTEM
2001 PRIUS (RM778U)
DTC 31, 41 Air Mix Damper Position Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the position of the air mix damper and
sends the appropriate signals to the A/C amplifier. The position
sensor is built into the air mix control servomotor.
DTC No.Detection ItemTrouble Area
31Short to ground or power source circuit in air mix damper posi-
tion sensor circuit.
Air mix damper position sensor.

Harness of connector between air mix control servomotor and
41Air mix damper position sensor value does not change even if
Harness of connector between air mix control servomotor and
A/C amplifier.41Air mix dam er osition sensor value does not change even if
A/C amplifier operates air mix control servomotor.
A/C amplifier.
WIRING DIAGRAM
DI7SC±01

I1907632 1COOL
WARM
DI±904
± DIAGNOSTICSAIR CONDITIONING SYSTEM
2001 PRIUS (RM778U)
2 Check air mix damper position sensor.
PREPARATION:
Remove air mix control servomotor (See page AC±56).
CHECK:
Measure resistance between terminals 1 and 2 of air mix control
servomotor connector.
OK:
Resistance : 4.2 ± 7.8 kW
CHECK:
While operating air mix control servomotor as shown in the pro-
cedure on page DI±906, measure resistance between termi-
nals 2 and 3 of air mix control servomotor connector.
OK:
PositionResistance
Max. COOL3.6 ± 6.7 kW
Max. WARM0.6 ± 1.1 kW
HINT:
As the air mix control servomotor moves from cool side to hot
side, the resistance decreases gradually without interruption.
NG Replace air mix control servomotor.
OK
3 Check harness and connector between A/C amplifier and air mix control servo-
motor (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace A/C amplifier.