fuse chart LEXUS SC400 1991 Service Repair Manual

IG Power Source Circuit
CIRCUIT DESCRIPTION
This is the power source for the air conditioner control assembly (contains\
the A/C control assembly)
and servomotor, ect.
DIAGNOSTIC CHART
WIRING DIAGRAM
Check voltage between terminals IG+ and E
of air conditioner control assembly
connector.
Check continuity between terminal E of air
conditioner control assembly and
body ground.
Check HTR fuse.
Check harness and repair and connector be-
tween air conditioner control assembly and
battery
Proceed to next circuit inspection
shown on matrix chart (See page
AC-36).
Check for short in all the harness
and components connected to
the HTR fuse (See attached wir -
ing diagram).
Repair or replace harness or
connector.
AC±70±
AIR CONDITIONING SYSTEM Troubleshooting
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Check voltage between terminals IG+ and E of air conditioner control
assembly connector.
(1) Remove console upper panel.(See pageBO-111 ).
(2) Remove A/C control assembly with connec±
tors still connected.
(3) Turn ignition switch ON.
Measure voltage between terminals IG+ and E of air
conditioner control assembly.
Voltage: 10 ±14 V
Proceed to next circuit inspection shown on matrix
chart (See page AC-36).
Check continuity between terminals E of air conditioner control assem-
bly and body ground.
Measure resistance between terminals E of air condi-
tioner control assembly and body ground.
Resistance:1  or less
Repair or replace harness or connector.
Remove HTR fuse from J/B No. 1.
Check continuity of HTR fuse
Continuity
Check HTR fuse.
Check for short in all the harness and
components connected to the HTR fuse
See attached wiring diagram).
Check and repair harness and connector between air conditioner control \
assembly and battery.
INSPECTION PROCEDURE
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AIR CONDITIONING SYSTEM TroubleshootingAC±71
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ACC Power Source Circuit
CIRCUIT DESCRIPTION
This circuit supplies power to the air conditioner control assembly (contai\
ns the A/C control assembly).
DIAGNOSTIC CHART
WIRING DIAGRAM
Check voltage between terminals ACC of air
conditioner control assembly connector
and body ground.
Check RADIO No. 2 fuse.
Check and repair harness and connector
between air conditioner control assembly
and battery.
Proceed to next circuit inspection
shown on matrix chart (See page
AC-36).
Check for short in all the harness
and components connected to
the RADIO No. 2 fuse (See
attached wiring diagram).
AC±72±
AIR CONDITIONING SYSTEM Troubleshooting
WhereEverybodyKnowsYourName

Check voltage between terminals ACC of air conditioner control
assembly connector and body ground.
(1) Remove console upper panel.(See page BO-111 ).
(2) Remove A/C control assembly with connec±
tors still connected.
(3) Turn ignition switch ON.
Measure voltage between terminals ACC of air
conditioner control assembly connector and body
ground.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on matrix
chart (See page AC-36).
Check RADIO No. 2 fuse.
Remove RADIO No. 2 fuse from J/B No. 1.
Check continuity of RADIO No. 2 fuse.
Continuity.
Check for short in all the harness and
components connected to the RADIO No. 2
fuse (See attached wiring diagram).
Check and repair harness and connector between air conditioner control \
assembly and battery.
INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±73
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\
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Back±up Power Source Circuit
CIRCUIT DESCRIPTION
This is the backup power source for the air conditioner control assembly. Power is supplied even when
the ignition switch is off and is used for diagnostic code memory, etc.
DIAGNOSTIC CHART
WIRING DIAGRAM
Check voltage between terminal B of air
conditioner control assembly connector
and body ground.
Check DOME fuse.
Proceed to next circuit inspection
shown on matrix chart (See page
AC-36
).
Check and repair harness and connector
between air conditioner control assembly
and battery.
Check for short all in the harness
and components connecteds to
the DOME fuse (See attached wiring
diagram)
AC±74±
AIR CONDITIONING SYSTEM Troubleshooting
WhereEverybodyKnowsYourName

Check voltage between terminals B of air conditioner control assembly
connector and body ground.
(1) Remove console upper panel.(See page BO-111 ).
(2) Remove A/C control assembly with connec±
tors still connected.
Measure voltage between terminals B of air condi-
tioner control assembly connector and body
ground.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on matrix
chart (See page AC-36).
Check DOME fuse.
Remove DOME fuse from R/B No. 2.
Check continuity of DOME fuse.
Continuity.
Check for short in all the harness and
components connected to the DOME fuse
(See attached wiring diagram).
Check and repair harness and connector between air conditioner control \
assembly and battery.
INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±75
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\
\


\

\
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Heater Main Relay Circuit
CIRCUIT DESCRIPTION
The heater main relay is switched on by signals from the air conditioner co\
ntrol assembly.
It supplies power to the blower motor.
DIAGNOSTIC CHART
Check voltage between terminals HR of air
conditioner control assembly connector
and body ground.
Check heater main relay.
Check HTR fuse.
Check and repair harness and connector
between air conditioner control assembly
and battery.
Proceed to next circuit inspection
shown on matrix chart (See page
AC-36
).
Check for short in all the harness
and components connected to
the HTR fuse (See
attached wiring diagram).
Replace heater main relay.
WIRING DIAGRAM
AC±76±
AIR CONDITIONING SYSTEM Troubleshooting
WhereEverybodyKnowsYourName

Check voltage between terminals HR of air conditioner control assem-
bly connector and body ground.
(1) Remove console upper panel.(See page BO-111 ).
(2) Remove A/C control assembly with connec±
tors still connected.
Proceed to next circuit inspection shown on ma-
trix chart (See page AC-36).
Check heater main relay.
Check continuity between each pair of terminals of
heater main relay shown below.
Measure voltage between terminals HR of air condi-
tioner control assembly and body ground when
ignition switch is on and off.
(1) Apply battery voltage between terminals 1
and 3
(2) Check continuity between each pair of ter±minal shown below.
Replace heater main relay.
Remove HTR fuse from J/B No. 1.
Check continuity of HTR fuse
Continuity
Check for short in all the harness and
components connected to the HTR fuse
See attached wiring diagram).
Check and repair harness and connector between air conditioner control \
assembly and battery.
INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±77
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OKNG
1
2
3
4
5
6
6
OK
OK
YES
YES NG
NG NO
NO
Check connection of center airbag sensor
assembly connector.
Preparation.
Check airbag warning light circuit.
Does airbag warning light come on?
Is new ECU ±B fuse burnt out again? GO to step
Repair.
Repair airbag warning light circuit
(See page BE±150).
Check terminal LA of center
airbag sensor assembly and
electrical connection check
mechanism. If normal, replace
center airbag sensor assembly.
Using simulation method,
reproduce malfunction symptoms
(See page IN±20).
Check harness between ECU ±B fuse and
airbag warning light, and ECU±B fuse and
center airbag sensor assembly. From the results of the above inspection,
the malfunctioning part can now be
considered normal. To make sure of this,
use the simulation method to check.
Check ECU ±B fuse.
DIAGNOSTIC CHART
Troubleshooting for this system is different for when the airbag warning light does not light up and for
when diagnostic code 22 is output. Confirm the problem symptoms first before\
selecting the appropriate
troubleshooting procedure.
HINT: If airbag warning light does not light up, perform the following troub\
leshooting:
±
SRS AIRBAG TroubleshootingAB±75
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OK
Check operation of airbag warning light.
NG1
WIRING DIAGRAM
2Is diagnostic code 41 output again? System is normal.
Check harness between ECU±B
fuse and center airbag sensor as-
sembly. If normal, replace center
airbag sensor assembly.
Perform troubleshooting according to
malfunction code output. NO
YES
Diag. Code 41Malfunction Stored in Memory
CIRCUIT DESCRIPTION
If a malfunction occurs in the airbag system, malfunction codes 11 to 31 may be output, and when the
battery is disconnected after the malfunction is repaired, malfunction codes 11 to 31 will be cleared,
but code 41 will be output instead.
So long as the cancellation operation for a malfunction stored in memory (\
See page
AB±32) is not per-
formed, code 41 is stored in the center airbag sensor assembly and the airbag w\
arning light remains
lit up.
Code No.Diagnosis
41
Malfunction recorded in memory.41
Center airbag sensor assembly malfunction.
DIAGNOSTIC CHART
AB±82±
SRS AIRBAG Troubleshooting
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