LEXUS SC400 1991 Service Repair Manual

RS±58
RS±59
RS±63RS±65
RS±67
RS±68
RS±63
RS±59
RS±59
RS±59
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±57
WhereEverybodyKnowsYourName

SRS WARNING LIGHT CHECK
DIAGNOSIS INSPECTION
(a) Turn the ignition switch to ACC or ON and check that the SRSwarning light lights up.
(b) Check that the SRS warning light goes out after approx. 6
seconds.
HINT:
wWhen the ignition switch is at ACC or ON and the SRS
warning light remains on, the TROUBLESHOOTING
has detected a malfunction code.
w If, after approx. 6 seconds have elapsed, the SRS
warning light sometimes lights up or the SRS warning
light lights up even when the ignition switch is OFF, a
short in the SRS warning light circuit can be considered
likely. Proceed to SRS warning light system (always lit
up when ignition switch LOCK position) on page
RS±119 .
DIAGNOSTIC TROUBLE CODE CHECK
Using diagnosis check wire:
1. OUTPUT DIAGNOSTIC TROUBLE CODE
(a) Turn the ignition switch to ACC or ON position and wait approx. 20 seconds.
(b) Using SST, connect terminals Tc and E of the DLC2. SST 09843±18020
NOTICE: Never make a mistake with the terminal connec-
tion position as this will cause a malfunction.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±59
WhereEverybodyKnowsYourName

2. READ DIAGNOSTIC TROUBLE CODERead the 2±digit diagnostic trouble code as indicated by the
number of times the SRS warning light blinks. As an example,
the blinking patterns; normal, 11 and 31 are as shown on the
illustration.
wNormal code indication
The light will blink 2 times per second.
w Malfunction code indication
In the event of a malfunction, the light will blink. The number
represented by the first blink code output indicates the first
digit of a 2±digit diagnostic trouble code. After a 1.5 second
pause, the second blink code will indicate the second digit.
If there are two or more codes, there will be a 2.5 second
pause between each.
After all the codes have been output, there will be a 4.0 se-
cond pause and they will all be repeated.
HINT:
w In the event of a number of trouble codes, indication will
begin from the smaller numbered code to the larger.
w If it does not output a diagnostic trouble code or output
a diagnostic trouble code without terminal connection,
proceed to the Tc terminal circuit inspection on page
RS±121 .
Using LEXUS hand±held tester: (a) Hook up the LEXUS hand±held tester to the DLC1 or DLC2.
(b) Read the diagnostic trouble codes by following the prompts on the tester screen.
HINT: Please refer to the LEXUS hand±held tester operator's
manual for further details.
RS±60
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

DIAGNOSTIC TROUBLE CODES
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±61
WhereEverybodyKnowsYourName

HINT:

When the SRS warning light remains lit up and the diagnostic trouble code in\
the normal code, this means a
source voltage drop.
This malfunction is not stored in memory by the center airbag sensor assembl\
y and if the power source voltage
returns to normal, after approx. 10 seconds the SRS warning light will automati\
cally go out.

Code 22 in recorded when a malfunction occurs in the SRS warning light syste\
m. If an open malfunction occurs
in the SRS warning light system, the SRS warning light does not light up\
. so that until the malfunction is repaired,
the diagnostic trouble codes (including code 22) cannot be confirmed.

When 2 or more codes are indicated, the lowest numbered code will appear\
first.

If a code not listed on the chart is displayed, then the center airbag s\
ensor assembly is faulty.
RS±62
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

DIAGNOSTIC TROUBLE CODE
CLEARANCE
Using diagnostic check wire:(a) Connect the 2 service wires to terminals Tc and AB of DLC1.
(b) Turn the ignition switch ACC or ON And wait approx. 6 seconds.
(c) Starting with the Tc terminal, apply body ground alternately to terminal Tc and terminal AB twice each in cycles of 1.0
seconds Confirm that body ground is absolute. Finally, keep
applying body ground to terminal Tc.
HINT: When alternately grounding terminals Tc and AB, re-
lease ground from one terminal and immediately apply it to
the other terminal within an interval of 0.2 second. If diagnos-
tic trouble codes do not clear, repeat the above procedure un-
til the codes are cleared.
(d) Several seconds after performing the clearing procedure, theSRS warning light will blink in a 50 m sec cycle to indicate the
codes have been cleared.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±63
WhereEverybodyKnowsYourName

Using LEXUS hand±held tester:(a) Hook up the LEXUS hand±held tester to the DLC1 or DLC2.
(b) Clear the diagnostic trouble codes by following the prompts on the tester screen.
HINT: Please refer to the LEXUS hand±held tester operator's
manual for further details.
RS±64
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName

SYMPTOM SIMULATION
ªIntermittent troubles or problemsº are the malfunctions about which the customer \
has a complaint, but which
do not occur and can not be confirmed in the workshop. The intermittent pr\
oblems also include complaints about
the SRS warning light going on and off erratically.
The self±diagnostic system stores the circuit of the intermittent pro\
blem in memory even if the ignition switch
is turned off.
And, for accurate diagnosis of the problems, ask the customer to obtain info\
rmation as much as possible follow-
ing the customer problem analysis check sheet (See page RS±58) and try to reproduce the intermittent problem.
The problem simulation methods described below are the effective ways for this nature of problem to produce
the problem conditions by applying vibration, heat, and humidity.
1VIBRATION METHOD: When vibration seems to be the major cause.
CONNECTORS
Slightly shake the connector vertically and horizontally.
(Inspection of connectors)
(a) Does the wire harness connecting with its corre-
sponding part have insufficient slack?
(b) Are the terminals dirty?
(c) Are the terminals making loose contact due to termi-
nals spread?
WIRE HARNESS
Slightly shake the wire harness vertically and horizontal-
ly. The connector joint, fulcrum of the vibration, and
body through portion are the major areas to be checked
thoroughly.
PARTS AND SENSORS
Apply vibration slightly by a finger to the part or sensor
considered to be the problem cause and check if the
malfunction will occur.
Caution: Do not apply vibration to the center
airbag sensor assembly.
±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTINGRS±65
WhereEverybodyKnowsYourName

2HEAT METHOD: When the problem seems to occur when the suspect area is heate\
d.
Heat the component that is likely the cause of the mal-
function with a hair dryer or similar object. Check to see
if the malfunction will occur.
Notice:

Do not heat to more than 60 C (140 F) (Tempera-
ture limit that the component can be touched with a
hand.)

Do not apply heat directly to any part in the ECU.
3WATER SPRINKLING METHOD: When the malfunction seems to occur on a rainy day or in
a high±humidity condition.
Sprinkle water onto the vehicle and check to see if the
malfunction will occur.
Notice: Never apply water directly onto the
electronic components.
HINT:

If the vehicle is subject to water leakage, the leaked
water may contaminate the ECU. When testing a ve-
hicle with a water leakage problem, special caution
must be paid.
4OTHER: When a malfunction seems to occur when electrical load is excessive.
Turn on all electrical loads including the heater blower,
headlights, rear window defogger, etc. and check to see
if the malfunction will occur.
RS±66±
SUPPLEMENTAL RESTRAINT SYSTEM TROUBLESHOOTING
WhereEverybodyKnowsYourName