LEXUS SC400 1991 Service Repair Manual

WIRE HARNESS AND CONNECTOR
RS01B±02
HINT: The SRS wire harness is integrated with the cowl wire
harness assembly and floor wire harness assembly.
The wires for the SRS wire harness are encased in a yellow
corrugated tube and all the connectors in the system are a
standard yellow color.
INSPECTION ITEMS
RS01C±0A
1. VEHICLES NOT INVOLVED IN A COLLISIONPerform a diagnostic system check.
(See page RS±59)
2. VEHICLES INVOLVED IN A COLLISION
(a) Perform a diagnostic system check.
(See page RS±59)
(b) If there is a break in any of the wires in the SRS wire harness,
or if conductors are exposed.
(c) In the SRS wire harness connectors are cracked or chipped.
±
SUPPLEMENTAL RESTRAINT SYSTEM WIRE HARNESS AND CONNECTORRS±47
WhereEverybodyKnowsYourName

REPLACEMENT REQUIREMENTS
RS01D±07
In the following cases, replace the wire harness or connector.
wIf any part of the SRS wire harness or any connector has
been found to be faulty in troubleshooting.
w If any part of the SRS wire harness or any connector has
been found to be faulty during the check in items 2±(b)
or (c).
NOTICE:
w If the wire harness used in the SRS is damaged, replace
the whole wire harness assembly.
w When the connector to the WIRE HARNESS AND CON-
NECTORs can be repaired alone (when there is no
damage to the wire harness), use the repair wire specially
designed for the purpose.
SENSOR REPLACEMENT
REPAIR WIRE FOR FRONT AIRBAG
RS04A±01
Repair wire with 2 pressure±contact sleeves
(Part No. 82988±24010) has been prepared for exclusive
use in repairing connector damage etc. caused by frontal col-
lision of the vehicle.
When repairing the WIRE HARNESS AND CONNECTOR
connector on the wire harness side, always use the special
repair wire.
NOTICE: Do not replace the connector housing or termi-
nal only.
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 ªLOCKº posi-
tion and the negative (±) terminal cable is disconnected
from the battery.
(See page RS±2)
2. DISCONNECT WIRE HARNESS AT VEHICLE SIDE
(a) Remove the cover at the rear of the connector housing and expose the wire harness.
(b) Cut the wire harness behind the connector housing. HINT: The operation is performed more easily if the wire har-
ness is left as long as possible.
RS±48
±
SUPPLEMENTAL RESTRAINT SYSTEM WIRE HARNESS AND CONNECTOR
WhereEverybodyKnowsYourName

3. CONNECT WIRE HARNESS AND CONNECTOR WIREHARNESS AT VEHICLE SIDE AND REPAIR WIRE
(a) Start stripping at least 8 mm (0.31 in.) to 11 mm (0.43 in.)
away from the end of the existing harness at vehicle side and
also from the end of the repair wire.
NOTICE: Take care not to damage the wire when strip-
ping the wire harness lead. After finishing the operation,
visually inspect the wire. If there is any damaged, per-
form the operation again.
(b) O v e r l a p t h e 2 s t r i pped wire ends inside of the
pressure±contact sleeve as illustrated in the left.
HINT: The blue pressure±contact sleeve
(Part No. 82999±12020) is available individually.
HINT: You might find it easier if you use a miniature screwdriv-
er as a guide as you insert wires into the sleeve.
(c) The crimping tool (AMP Part No. 169060) has color marks on it. Place the sleeve in the correct section of the tool according
to the color of the sleeve itself.
±
SUPPLEMENTAL RESTRAINT SYSTEM WIRE HARNESS AND CONNECTORRS±49
WhereEverybodyKnowsYourName

(d) With the center of the sleeve correctly placed between thecrimping jaws, squeeze the crimping tool until either end
comes into contact at the section marked by ªCLOSE HEREº.
HINT: Check to see that the sleeve and wires are still in the
correct position before closing the crimping tool ends with
steady pressure.
(e) Pull the joined wires to either end. Make sure that they are joined firmly by the sleeve.
NOTICE: If the joined wires come loose the splice is de-
fective, so replace the sleeve and repeat the procedure.
(f) Crimp both ends of the sleeve with the crimping tool at the ªINSº position.
4. PROTECT JOINED SECTION Wrap silicon tape around the joins to protect them from water.
HINT:
wBefore starting the operation, throughly wipe dirt and
grease off the sections to be joined.
w If the adhesive surfaces of 2 tapes come in contact, they
will stick together and will not come apart, so do not
remove the backing film except when using the tape.
w Do not let oil and dust, etc., get on the tape surface.
(a) Ready about 100 mm (3.94 in.) of silicon tape (Part No. 08231±00045) and peel off the film.
(b) Stretch the silicon tape until its width is reduced by half.
(c) About 10 mm (0.39 in.) from the end of the pressure contact
sleeve, wrap the silicon tape around the sleeve 3 or more
times while stretching the tape.
RS±50
±
SUPPLEMENTAL RESTRAINT SYSTEM WIRE HARNESS AND CONNECTOR
WhereEverybodyKnowsYourName

(d) Wrap the remaining part of sleeve with half of the tapeoverlapping at each turn.
(e) Firmly wrap the tape 2 times or more about 10 mm (0.39 in.)
from the other end of the pressure±contact sleeve, then wrap
the tape back towards the start again and firmly finish winding
the tape around the center of the sleeve.
(f) Fix the corrugated tube to the wire using silicon tape.
(g) After applying the s ilicon tape, apply vinyl tape on the
corrugated tube of repair wire side over to the corrugated
tube of vehicle wire harness side.
5. CONNECT NEGATIVE (±) TERMINAL CABLE TO BATTERY
±
SUPPLEMENTAL RESTRAINT SYSTEM WIRE HARNESS AND CONNECTORRS±51
WhereEverybodyKnowsYourName

± MEMO ±
RS±52
±
SUPPLEMENTAL RESTRAINT SYSTEM WIRE HARNESS AND CONNECTOR
WhereEverybodyKnowsYourName

TROUBLESHOOTING
 HOW TO PROCEED WITH 
 TROUBLESHOOTING RS±54 CUSTOMER PROBLEM ANALYSIS CHECK SHEET RS±58 DIAGNOSIS INSPECTION RS±59 SYMPTION SIMULATION RS±65 DIAGNOSTIC TROUBLE CODE MATRIX CHART RS±67 PROBLEM SYMPTOM CHART RS±67 CIRCUIT INSPECTION RS±68 DTC (Normal) RS±68 DTC 11 RS±70 DTC 12 RS±78 DTC 13 RS±85 DTC 14 RS±92 DTC 15 RS±97 DTC 22 RS±102 DTC 31 RS±108 DTC 53 RS±110 DTC 54 RS±115 SRS Warning Light System (Always Lit Up, when ignition switch is Lock position) RS±119 Tc Terminal Circuit RS±121
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±53
WhereEverybodyKnowsYourName

HOW TO PROCEED WITH TROUBLESHOOTING
Malfunction symptoms of the supplemental restraint system are difficult to confirm, so the diagnostic
trouble codes become the most important source of information when troubleshoot\
ing. Perform trouble-
shooting of the supplemental restraint system in accordance with the fol\
lowing procedure:
HINT: Do not disconnect the battery negative (±) terminal cable until st\
ep , Diagnostic Trouble Code
Check and Recording, has been completed.

CUSTOMER PROBLEM ANALYSIS
Using the CUSTOMER PROBLEM ANALYSIS CHECK SHEET (See page RS±58) for reference, ask the
customer in as much detail as possible about the problem.
WARNING LIGHT CHECK
Check the SRS warning light. If the light remains on, a malfunction is stored in the center airbag sensor,
assembly, so proceed to step . If the SRS warning light is not on, a malfunction has occurred in the SRS
warning light circuit, so perform troubleshooting for 22.
HINT: 22 is recorded when a malfunction occurs in the SRS warning light syst\
em.
If an open malfunction occurs in the SRS warning light system, the SRS w\
arning light does not light up,
so that until the malfunction is repaired, the diagnostic trouble codes (\
including 22) cannot be confirmed.
 DIAGNOSTIC TROUBLE CODE CHECK AND RECORDING
Check the di agnostic trouble codes and make a note of any malfunction codes which ar\
e output. If a normal
code is output, an abnormality in the power source circuit may have occurred\
, so perform troubleshooting
for source voltage in step .
If 22 is output, skip steps  and  and proceed to step .
 MALFUNCTION CODE CLEARANCE
Clear the malfunction code.
HINT: The malfunction code output in step  indicates that a malfunction has occurred in the circuit desig-
nated by the malfunction code, but does not indicate whether the malfunction \
is still occurring or whether
it was in the past.
Accordingly, it is necessary to find out the present condition of the malfunction oc\
currence by clearing the
malfunction code and performing the diagnostic code check again. If this\
operation is neglected and trou-
bleshooting is performed using only the malfunction code confirmed in step , isolating the problem com-
ponent becomes difficult and invites mistaken diagnosis.
 DIAGNOSTIC TROUBLE CODE CHECK AND RECORDING  SYMPTOM SIMULATION
After repeating ignition switch ON±OFF operation (ON: wait 20 secs, OFF: \
wait 20 secs.) 5 times, check
the diagnostic trouble codes. If any code is output, the malfunction is sti\
ll occurring, so proceed to step .
Bearing in mind that a malfunction code was registered in step , provided that the normal code is present-
ly output, use the methods described in step  to simulate the malfunction.
RS±54
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

NOTICE: When connecting the battery after clearing the malfunction code, always\
do it with the igni-
tion switch in LOCK position. When the battery has been reconnected, turn the ignition switch to
ACC or ON position after at least 2 seconds have elapsed.
If the battery is reconnected with the ignition switch in ACC or ON posi\
tion, or the ignition switch
is turned to ACC or ON within 2 seconds of connecting the battery, it is possible that the diagnosis
system will not operate normally.
 DIAGNOSTIC TROUBLE CODE CHART
Proceed to the appropriate flow chart in step  in accordance with the malfunction code found in step 
or .
 CIRCUIT INSPECTION \b REPAIR
Find out if the problem lies in a sensor, actuator or TROUBLESHOOTING, and repair the problem. After
the problem part is repaired, reinstall the disassembled parts. Do not s\
tart work until at least 90 seconds
after the ignition switch is turned to the LOCK position and the negative (±\
) terminal cable is disconnected.
CAUTION: If incorrect procedure is used, a malfunction may occur in the system o\
r there is the dan-
ger that airbag may be accidentally deploy during the repair operation. \
Carefully read the GENERAL
DESCRIPTION (See page RS±2) and the cautions for each operation, and perform repairs in the cor-
rect order using the correct methods.
HINT: The following illustration for the CIRCUIT INSPECTION shows each conne\
ctor for the SRS squib
circuit.
 
















 
















 
















±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±55
WhereEverybodyKnowsYourName

10 MALFUNCTION CODE CLEARANCEWhen all the malfunction codes found in steps  and  have been repaired, clear the malfunction codes.
11 DIAGNOSTIC TROUBLE CODE CHECK
After repeating ignition switch ON±OFF operation (ON: wait 20 secs, OFF: \
wait 20 secs.) 5 times, check
the diagnostic trouble codes. If a code is displayed, return to step  and troubleshoot the displayed mal-
function code.
NOTICE: When connecting the battery after clearing the malfunction code, always\
do it with the igni-
tion switch in LOCK position. When the battery has been reconnected, turn the ignition switch to
ACC or ON position after at least 20 seconds have elapsed.
If the battery is reconnected with the ignition switch in ACC or ON posi\
tion, or the ignition switch
is turned ACC or ON within 20 seconds of connecting the battery, it is possible that the diagnosis
system will not operate normally.
12 CONFIRMATION TEST Check the warning light again and confirm that all the malfunctions have been\
repaired. If the warning light
indicates an abnormality, repeat the operation again from step .
RS±56
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName