1991 LEXUS SC400 fuse chart

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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CIRCUIT INSPECTION
+B Power Source Circuit
CIRCUIT DESCRIPTION
This is the power source for motors such as the slide motor and reclining mo\
tor.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Check Door fuse.NG
Check for short in all harness and
components connected to the
DOOR fuse (See attached wiring
diagram).
Check voltage between terminals +B, +B2
and GND of ECU connector. OK
OKProceed to next circuit inspection
shown on matrix chart (See page
BE±276
).
Check continuity between terminal GND
of ECU connector and body ground. NG
NGRepair or replace harness or
connector.
OK
Check and repair harness or connector
between ECU and battery.
WIRING DIAGRAM
BE±284±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
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OKNG
NGOK
OKNG
INSPECTION PROCEDURE
1Check DOOR fuse.
Check for short in all the harness and components con-
nected to the DOOR fuse (See attached wiring diagram).
2Check voltage between terminals +B, +B2 and GND of ECU connector.
C
OK
PRemove ECU with connectors still connected.
Measure voltage between terminals +B, +B2 and GND
of ECU connector.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on matrix chart
(See page BE±276.)
3Check continuity between terminal GND of ECU connector and body ground.
C
OK
Measure resistance between terminal GND of ECU and
body ground.
Resistance: 1
or less.
Repair or replace harness or connector.
Check and repair harness or connector between
ECU and battery.
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)BE±285
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WIRING DIAGRAM
ECU Power Source Circuit
CIRCUIT DESCRIPTION
This circuit provides power for ECU operation and is also the power source f\
or the sensors.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Check DOME fuse.NGCheck for short in all the harness
and components connected to
DOME fuse.
(See attached wiring diagram).
OK
Check voltage between terminals SYSB
and SGND of ECU connector. Proceed to next circuit inspection
shown on matrix chart
(See page
BE±276).
Check continuity between terminal SGND
of ECU connector and body ground. OK
NG
OK NG
Replace or repair harness or
connector.
Check and repair harness or connector
between ECU and battery.
BE±286±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
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OKNG
NGOK
OKNG
INSPECTION PROCEDURE
1Check DOME fuse.
Check for short in all the harness and components con-
nected to the DOME fuse (See attached wiring diagram).
2Check voltage between terminals SYSB and SGND of ECU connector.
C
OK
PRemove ECU with connectors still connected.
Measure voltage between terminals SYSB and SGND
of ECU connector.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on matrix chart
(See page BE±276).
3Check continuity between terminal SGND of ECU connector and body ground.\
C
OK
Measure resistance between terminal SGND of ECU
connector and body ground.
Resistance: 1
or less.
Repair or replace harness or connector.
Check and repair harness or connector between
ECU and battery.
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)BE±287
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WIRING DIAGRAM
Ignition Switch Circuit
CIRCUIT DESCRIPTION
This circuit sends an ignition switch ON or OFF signal to the ECU.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Check ECU±IG fuse.NG
Check for short in all the harness
and components connected to
ECU±IG fuse.
Check voltage between terminal IG of
ECU connector and body ground. OK
OK
NG Proceed to next circuit inspection
shown on matrix chart
(See page
BE±276).
Check and repair harness or connector
between ECU and battery (See page IN±27).
BE±302±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)
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OKNG
NGOK
INSPECTION PROCEDURE
1Check ECU ± IG fuse.
Check for short in all the harness and components con-
nected to ECU±IG fuse.
2Check voltage between terminal IF of ECU connector and body ground.
C
PRemove ECU with connectors still connected.
Measure voltage between terminal IG of ECU connector
and body ground when ignition switch is on and off.
Ignition switch Voltage
ON
OFF 10 ± 14 V
Below 1 V
Proceed to next circuit inspection shown on matrix chart
(See page BE±276).
Check and repair harness or connector between
ECU and battery (See page IN±27).
±
BODY ELECTRICAL SYSTEM Power Seat Control System (Driver's Seat)BE±303
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