2001 TOYOTA PRIUS air conditioning

I18168
IG
(±) (+) ON
I18167
GND
(±) (+)
DI±922
± DIAGNOSTICSAIR CONDITIONING SYSTEM
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check voltage between terminals IG and GND 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 IG and GND of A/C amplifi-
er.
OK:
Voltage : 10 ± 14 V
OK Proceed to next circuit inspection shown on
problem symptoms table (See page DI±874).
NG
2 Check continuity between terminal GND of A/C amplifier and body ground.
CHECK:
Measure resistance between terminal GND of A/C amplifier and
body ground.
OK:
Resistance : Below 1 W
NG Repair or replace harness or connector.
OK

I18410
Instrument Panel J/B
HTR Fuse
± DIAGNOSTICSAIR CONDITIONING SYSTEM
DI±923
2001 PRIUS (RM778U)
3 Check HTR fuse.
PREPARATION:
Remove HTR fuse from instrument panel J/B.
CHECK:
Check continuity of HTR fuse.
OK:
Continuity exists.
NG Check for shot in all the harness and compo-
nents connected to the HTR fuse.
OK
Check and repair harness and connector between A/C amplifier and battery.

I18385
A/C Amplifier
A78 ECU±B
F
1W
F11
FL Block No. 1 DC/DC
Battery+B Instrument Panel J/B
R±G J25
J/C
MAINR±GF
2C5
2H1
1F13
B±G
F18
FL Block No. 2 DI±924
± DIAGNOSTICSAIR CONDITIONING SYSTEM
2001 PRIUS (RM778U)
Back Up Power Source Circuit
CIRCUIT DESCRIPTION
This is the back±up power source for the A/C amplifier. Power is supplied even when the ignition switch is
off.
WIRING DIAGRAM
DI7SJ±01

I18172
+B
(+) (±)
I18410
ECU±B Fuse Instrument Panel J/B
± DIAGNOSTICSAIR CONDITIONING SYSTEM
DI±925
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check voltage between terminal +B of A/C amplifier connector and body ground.
PREPARATION:
Remove A/C amplifier with connectors still connected.
CHECK:
Measure voltage between terminal +B of A/C amplifier connec-
tor and body ground.
OK:
Voltage : 10 ± 14 V
OK Proceed to next circuit inspection shown on
problem symptoms table (See page DI±874).
NG
2 Check ECU±B fuse.
PREPARATION:
Remove ECU±B fuse from instrument panel J/B.
CHECK:
Check continuity of ECU±B fuse.
OK:
Continuity exists.
NG Check for short in all the harness and compo-
nents connected to the ECU±B fuse (See page
IN±41).
OK
Check and repair harness and connector between A/C amplifier and battery.

I18388
A/C Amplifier
11
A7MPX+ GR
4
MPX+
BJ6
J/C
HTR Relay
J/C
Battery4
A7
MP2+ C11
Combination Meter
MPX±
11 GR±B
MPX1 MPX2
10
B8
14 13
11
B8 MPX+
MPX±
MPD2
MPD1
Instrument Panel J/B
HRLY6
2FL±O
BR R 4
1F
5 3
2
HTR
13
1J
8
1K
3
1B
3
1K
To Blower Motor
W13
IE1
R
A
J23
CJ22
R
FL Block
No. 1 DC/DC
B±G
F11 1
F13 1
1
MAINW±B
A F18
FL Block
No. 2
AWInstrument Panel J/B
1
2H
8
2K
IG1
Relay
3
25
1AM1
W±GI15
Ignition
SW
HTRAM1
3
2B
6
2D
3
2D
IG12
4
B±Y
J11
J/C
ID
IE W±BA
AJ1
J/C
3 2
E10 E10ECM
GR
GR±LC1
Gateway ECU
GR±B
J7 J/C
Engine Room J/B Body ECU DI±926
± DIAGNOSTICSAIR CONDITIONING SYSTEM
2001 PRIUS (RM778U)
Heater Main Relay Circuit
CIRCUIT DESCRIPTION
The heater main relay is switched on by signals from the A/C amplifier. It supplies power to the blower motor.
WIRING DIAGRAM
DI7SK±01

BE1850 BE1844I00312125
3
125
3
4
4
I18394
Engine Room J/B
HTR
Fuse
± DIAGNOSTICSAIR CONDITIONING SYSTEM
DI±927
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check heater main relay.
PREPARATION:
Remove heater main relay from engine room J/B.
CHECK:
Check continuity between each pair of terminals of heater main
relay shown below.
OK:
Tester connectionSpecified condition
1 ± 4No continuity
2 ± 4Continuity
3 ± 562.5 ± 90.9 W
PREPARATION:
Apply battery positive voltage between terminals 3 and 5.
CHECK:
Check continuity between each pair of terminal shown below.
OK:
Tester connectionSpecified condition
1 ± 2Continuity
2 ± 4No continuity
NG Replace hater main relay.
OK
2 Check HTR fuse
PREPARATION:
Remove HTR fuse from engine room J/B.
CHECK:
Check continuity of HTR fuse.
OK:
Continuity exists.
NG Check for short in all the harness and compo-
nents connected to the HTR fuse (See page
IN±41).
OK

DI±928
± DIAGNOSTICSAIR CONDITIONING SYSTEM
2001 PRIUS (RM778U)
3 Check harness and connector between heater main relay and body ground, heat-
er main relay and body ECU (See page IN±41).
NG Check and replace harness and connector.
OK
Check multiplex communication system (See page DI±750).

Duty Ratio =A + BA
x 100 (%)
ON
OFFA
B
1 cycle
Blower Level
0
Si duty (%)
LO M1M2HI
3043
67100
I18383
B7
Blower Motor Liner ControllerA/C Amplifier
B6 Blower Motor J2A21
C
A73
BLW
From
HTR RelayV IE1
V C J6
J/C
V
J2ASI
GND
+B J/C
J3A
VMW±B
A
J1
J/C
IE
± DIAGNOSTICSAIR CONDITIONING SYSTEM
DI±929
2001 PRIUS (RM778U)
Blower Motor Circuit
CIRCUIT DESCRIPTION
The blower motor is operated by signals from the A/C amplifier.
Blower motor speed signals are transmitted by changes in the
Duty Ratio.
Duty Ratio
The duty ratio is the ratio of the period of continuity in one cycle.
For example, if A is the period of continuity in one cycle, and B
is the period of non±continuity, then.
WIRING DIAGRAM
DI7SL±01