1991 LEXUS SC400 wiring

6. INSTALL STEERING WHEEL
(a) Align matchmarks on the steering wheel and main shaft, andinstall the steering wheel to the main shaft.
(b) Install and torque the set nut.
Torque: 35 N Vm (360 kgf Vcm, 26 ft Vlbf)
(c) Connect the connector.
7. INSTALL STEERING WHEEL PAD
(a) Connect the SRS connector.
(b) Install the wheel pad after confirming that the circumference
groove of the torx screws is caught on the screw case.
(c) Using a torx wrench, tighten the 4 screws.
Torque: 7.4 N Vm (75 kgf Vcm, 65 in. Vlbf)
NOTICE:
w Make sure the wheel pad is installed to the specified
torque.
w If the wheel pad has been dropped, or there are cracks,
dents or other defects in the case or connector, replace
the wheel pad with a new one.
w When installing the wheel pad, take care that the wirings
do not interfere with other parts and are not pinched
between other parts.
8. CHECK STEERING WHEEL CENTER POINT
9. CONNECT NEGATIVE (±) TERMINAL CABLE TO
BATTERY
RS±20
±
SUPPLEMENTAL RESTRAINT SYSTEM STEERING WHEEL PAD AND SPIRAL CABLE
WhereEverybodyKnowsYourName

COMPONENTS
RS043±01
FRONT PASSENGER AIRBAG
ASSEMBLY REMOVAL AND
INSTALLATION
RS044±01
NOTICE:
wIf the wiring connector of the supplemental restraint
system is disconnected with the ignition switch at ON or
ACC, diagnostic trouble codes will be recorded.
w Never use airbag parts from another vehicle. When
replacing parts, replace with new parts.
RS±30±
SUPPLEMENTAL RESTRAINT SYSTEM FRONT PASSENGER AIRBAG ASSEMBLY
WhereEverybodyKnowsYourName

5. REMOVE GLOVE COMPARTMENT DOOR LOCKMOUNTING BRACKET
Remove the 2 screws, disconnect the door lock mounting
bracket.
(a) Remove the 3 screws, 2 nuts and bolt.
6. REMOVE FRONT PASSENGER AIRBAG ASSEMBLY
(b) Pull out the front pass enger airbag assembly from the
instrument panel.
NOTICE: When removing the front passenger airbag as-
sembly, take care not to pull the airbag wire harness.
CAUTION:
w When storing the front passenger airbag assembly, keep
the upper surface of the front passenger airbag assembly
facing upward.
w Never disassemble the front passenger airbag assembly.
7. INSTALL FRONT PASSENGER AIRBAG ASSEMBLY
(a) Install and torque the 2 nuts and the bolt.
Torque: 21 N Vm (210 kgf Vcm, 15 ft Vlbf)
(b) Install the 3 screws.
NOTICE:
w Make sure the front passenger airbag assembly is
installed to the specified torque.
w If the front passenger airbag assembly has been
dropped, or there are cracks, dents or other defects in the
case or connector, replace the front passenger airbag
assembly with a new one.
w When installing the front passenger airbag assembly,
take care that the wiring do not interfere with other parts
and are not pinched between other parts.
RS±32±
SUPPLEMENTAL RESTRAINT SYSTEM FRONT PASSENGER AIRBAG ASSEMBLY
WhereEverybodyKnowsYourName

COMPONENTS
RS045±01
FRONT AIRBAG SENSOR
REMOVAL AND INSTALLATION
RS046±01
NOTICE:
wIf the wiring connector of the supplemental restraint
system is disconnected with the ignition switch at ON or
ACC, diagnostic trouble codes will be recorded.
w Never use SRS parts from another vehicle. When
replacing parts, replace with new parts.
w Never reuse the sensor involved in a collision when the
SRS has deployed.
w Never repair a sensor in order to reuse it.
RS±42±
SUPPLEMENTAL RESTRAINT SYSTEM FRONT AIRBAG SENSOR
WhereEverybodyKnowsYourName

CENTER AIRBAG SENSOR ASSEMBLY
REMOVAL AND INSTALLATION
RS049±01
NOTICE:
wDo not open the cover or the case of the ECU and various
computers unless absolutely necessary. (If the IC
terminals are touched, the IC may be destroyed by static
electricity.)
w Never use SRS parts from another vehicle. When
replacing parts, replace with new parts.
w Never reuse the center airbag sensor assembly involved
in a collision when the airbag has deployed.
w Never repair a sensor in order to reuse it.
1. DISCONNECT NEGATIVE (±) TERMINAL CABLE FROM
BATTERY
CAUTION: Work must be started after 90 seconds from
the time the ignition switch is turned to the LOCK posi-
tion and the negative (±) terminal cable is disconnected
from the battery (See page RS±2).
2. REMOVE AND INSTALL CENTER AIRBAG SENSOR ASSEMBLY
(a) Using a torx wrench, loosen and tighten the 3 screws.
Torx wrench: T40 (Part No. 09042±00020 or locally manufac-
tured tool)
(b) Disconnect and connect the connector. NOTICE: Removal and installation of the connector is
done with the sensor assembly installed.
(c) Using a torx wrench, tighten the 3 screws. Torx wrench: T40 (Part No. 09042±00020 or locally manufac-
tured tool)
Torque: 15 N Vm (150 kgf Vcm, 11 ft Vlbf)
NOTICE:
w Make sure the sensor assembly is installed to the
specified torque.
w If the sensor assembly has been dropped, or there are
cracks, dents or other defects in the case, bracket or
connector, replace the sensor assembly with a new one.
w When installing the sensor assembly, take care that the
airbag wiring does not interfere with other parts and is
not pinched between other parts.
w After installation, shake the sensor assembly to check
that there is no looseness.
RS±46±
SUPPLEMENTAL RESTRAINT SYSTEM CENTER AIRBAG SENSOR ASSEMBLY
WhereEverybodyKnowsYourName

WIRING DIAGRAM
CIRCUIT INSPECTION
DTC(Normal)Source Voltage Drop
CIRCUIT DESCRIPTION
The supplemental restraint system is equipped with a voltage ± increase \
circuit (DC±DC converter) in the center
airbag sensor assembly in case the source voltage drops.
When the battery voltage drops, the voltage ± increase circuit (DC±DC\
converter) functions to increase the volt-
age of the supplemental restraint system to normal voltage.
The diagnosis system malfunction display for this circuit is different to other circuits ± when the SRS warning
light remains lit up and the diagnostic trouble code is a normal code, source\
voltage drop is indicated. Malfunc-
tion in this circuit is not recorded in the center airbag sensor assembly, and approx. 10 seconds after the source
voltage returns to normal, the SRS warning light automatically goes off.
DTC No.Diagnosis
(Normal)Source voltage drop.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
(See page CH±1).
RS±68±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

WIRING DIAGRAM
DIAGNOSTIC CHART (Cont'd)DIAGNOSTIC CHART (Cont'd)
(See page RS±49).
RS±72±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

WIRING DIAGRAM
DTC12
wShort in Squib Circuit of Front Airbag Sensor Circuit
(to B+)
w Open in Front Airbag Sensor Circuit
CIRCUIT DESCRIPTION
The squib circuit consists of the center airbag sensor assembly, spiral cable and the steering wheel pad (squib).
It causes the SRS to deploy when the SRS deployment conditions are satisfi\
ed.
The front airbag sensor detects the deceleration force in a frontal collisi\
on and is located in the front fender on
the left and right sides.
For details of the function of each component, see FUNCTION OF COMPONENTS o\
n page RS±10. Diagnostic
trouble code 12 is recorded when a B+ short is detected in the squib circuit or\
the front airbag sensor circuit.
DTC No.Diagnosis
12
 Short circuit in squib wire harness (to B+)
 Squib malfunction
 Short circuit in front airbag sensor +S wire harness (to B+)
 Open circuit in RH and LH front airbag sensor harness.
 Spiral cable malfunction
 Center airbag sensor assembly malfunction
RS±78±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName