tdcl LEXUS SC300 1991 Service Repair Manual

ABBREVIATIONS USED IN THIS
MANUAL
ABS Anti±Lock Brake System J/B Junction Block
A/C Air Conditioner LED Light Emitting Diode
ALR Automatic Locking Retractor LH Left±Hand
APPROX. Approximation LHD Left±Hand Drive
A/T, ATM Automatic Transmission LLC Long Life Coolant (Year Around Coolant)
ATF Automatic Transmission Fluid Max. Maximum
BTDC Before Top Dead Center Min. Minimum
BVSV Bimetal Vacuum Switching Valve MP Multipurpose
CALIF. Vehicles Sold in California N Neutral
CB Circuit Breaker OD, O/D Overdrive
DOHC Double Over Head Cam O/S Oversize
DP Dash Pot P & BV Proportioning and Bypass Valve
ECT Electronic Controlled Transmission PCV Positive Crankcase Ventilation
ECU Electronic Controlled Unit PS Power Steering
EFI Electronic Fuel Injection RH Right±Hand
EGR Exhaust Gas Recirculation RL Rear Left
ELR Emergency Locking Retractor RR Rear Right
EPR Evaporator Pressure Regulator RR, Rr Rear
ESA Electronic Spark Advance SRS Supplemental Restraint System
EVAP Evaporative (Emission Control) SSM Special Service Materials
EX Exhaust (manifold, valve) SST Special Service Tools
Ex. Except STD Standard
FIPG Formed in Place Gasket SW Switch
FL Front Left TDC Top Dead Center
FL Fusible Link TDCL Total Diagnostic Communication Link
FPU Fuel Pressure Up Temp. Temperature
FR Front Right TRAC Traction Control System
FR, Fr Front TWC Three±Way Catalyst
HAC High Altitude Compensation VSV Vacuum Switching Valve
IG Ignition VTV Vacuum Transmitting Valve
IN Intake (manifold, valve) w/ With
INT Intermittent w/o Without
ISC Idle Speed Control
IN±34±
INTRODUCTION Abbreviations Used in This Manual
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TOTAL DIAGNOSTIC
COMMUNICATION LINK (TDCL)
The TDCL is provided inside the cabin (located under the left side
instrument panel) as a connector exclusively for diagnosis of data
from the engine, ECT, ABS, A/C, Airbag and Cruise Control Sys-
tem to improve serviceability. The check connector inside the en-
gine compartment is used for engine adjustment.
Connecting the following terminals of the TDCL to terminal E1 se-
lects the diagnosis mode shown.
NOTICE: Never make a mistake with the terminal connection
position as this will cause a malfunction.
TerminalSystem
TE1Engine and ECT (Normal mode)
TE2 and TE1Engine and ECT (Test mode)
TcABS, A/C, Airbag, Traction Control and Cruise
Control System
TTECT
Refer to the respective system for the inspection method.
HINT: By connecting the TDCL up to a monitor specifically de-
signed for use with the TDCL, the diagnosis result for each system
can be read easily.
±
INTRODUCTION Total Diagnostic Communication Link (TDCL)IN±7
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\
\


\

\
\
Diagnosis Circuit
CIRCUIT DESCRIPTION
This circuit sends signals to the A/C control assembly requesting output of \
diagnostic codes.
DIAGNOSTIC CHART
WIRING DIAGRAM
Check voltage between terminals Tc and
E1 of TDCL.
Check harness and connector between air
conditioner control assembly and TDCL and
body ground.
Proceed to next circuit inspection
shown on matrix chart (See page
AC-36
).
Repair or replace harness or
connector.
Check and replace air conditioner control
assembly.
AC±98±
AIR CONDITIONING SYSTEM Troubleshooting
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Check voltage between terminal Tc and E1 of TDCL.
(2) Check voltage between terminals Tc and E1 of TDCL.
Voltage: 10 ± 14 V
(1) Turn ignition switch on.
Proceed to next circuit inspection shown on
matrix chart. ( See page AC-36).
Check for open and short in harness and connector between air conditioner con-
trol assembly and TDCL, TDCL and body ground.(See page IN-27).
Repair or replace harness or connector.
Check and replace air conditioner control
assembly.
INSPECTION PROCEDURE
±
AIR CONDITIONING SYSTEM TroubleshootingAC±99
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Check center airbag sensor assembly.
Diagnostic code 14 is not output.(1) Connect connector to center airbag sensor
connector.
(2) Connect connector between center airbag sensor assembly and spiral cable.
(3) Using a service wire, connect D+ and D± on spiral cable side of connector between spiral
cable and steering wheel pad.
(4) Connect negative (±) terminal cable to battery,
and wait at least 2 seconds.
Check squib.
(1) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(2) Using SST, connect terminals Tc and E1 of TDCL.
SST 09843±18020
(3) Check diagnostic code.
(1) Turn ignition switch LOCK.
(2) Disconnect battery negative (±) terminal cable, and wait at least 20 seconds.
(3) Connect steering wheel pad (squib) connector.
(4) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
Diagnostic code 14 is not output. (1) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(2) UsingSST, connect terminals Tc and E1 of TDCL.
SST 09843±18020
(3) Check diagnostic code. Codes other than code 14 may be output at this
time, but this is not relevant to this check
Codes other than code 14 may be output at this
time, but this is not relevant to this check Replace steering wheel pad.
From the results of the above inspection, the malfunctioning part can no\
w be considered normal.
To make sure this, use the simulation method to check. Replace center airbag sensor assembly.
AB±66±
SRS AIRBAG Troubleshooting
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3
Codes other than code 15 may be output at this
time, but this is not relevant to this check.Replace front airbag sensor.
NG
OK
(1) Turn ignition switch ACC or ON, and wait at least 20
seconds.
(2) Using SST, connect terminals Tc and E
1 of TDCL.
SST 09843±18020
(3) Check diagnostic code.
Check center airbag sensor assmbly.
Check front airbag sensor.
Replace center airbag sensor assembly.NG
OK
Diagnostic code 15 is not output.
(1) Connect connector to center airbag sensor
assembly.
(2) Using a service wire, connect D+ and D± on spiral cable side of connector between spiral
cable and steering wheel pad.
(3) Connect negative (±) terminal cable to battery, and wait at least 2 seconds.
From the results of the above inspection, the malfunctioning part can no\
w be considered normal.
To make sure of this, use the simulation method to check.
4
Disconnect front airbag sensor connector. Measure resistance between each terminal of
front airbag sensor.

Do not touch ohmmeter probes strongly
against terminals of front airbag sensor.

Make sure the front airbag sensor connector
is properly connected.
Terminal Resistance
Below 1 
755
 ±885 
1 M or higher
+S ± +A
+S ± ±S
±S ± ±A
±
SRS AIRBAG TroubleshootingAB±71
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Diag. Code 22Airbag Warning Light System Malfunction
CIRCUIT DESCRIPTION
The airbag warning light is located on the combination meter.
When the airbag system is normal, the airbag warning light lights up for\
approx. 6 seconds after the
ignition switch is turned from LOCK position to ACC or ON position, and then turns off automatically.
If there is a malfunction in the airbag system, the airbag warning light\
lights up to inform the driver of
the abnormality.
When terminals Tc and E of the TDCL are connected, the diagnostic code is displayed by t\
he blinking
of the airbag warning light.
The airbag warning light circuit is equipped with an electrical connecti\
on check mechanism which
detects when the connector to the center airbag sensor assembly is not p\
roperly connected.
If the connector to the center airbag sensor assembly is not properly co\
nnected, the airbag warning
light will not light up.
Diagnostic code 22 is recorded when a malfunction occurs in the airbag w\
arning light system.
If an OPEN malfunction occurs in the airbag warning light system, the ai\
rbag warning light does not
light up, so that until the malfunction is repaired, the diagnostic code\
s (including code 22) cannot be
confirmed.
Code No.Diagnosis
22
Open circuit in airbag warning light system.22
Center airbag sensor assembly malfunction.
AB±74±
SRS AIRBAG Troubleshooting
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1
Using simulation method, reproduce malfunction
symptoms (See page IN±20).NO
YES
(1) Turn ignition switch LOCK, and wait at least 2
seconds.
(2) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(3) Using SST, connect terminals Tc and E
1 of TDCL.
SST 09843±18020
(4) Check diagnostic code. Clear malfunction code 41 stored in memory
(See page
AB±35).
Is diagnostic code 22 output again?
Replace center airbag sensor assembly.
HINT: If diagnostic code 22 is output, perform the following troubleshooting\
:
±
SRS AIRBAG TroubleshootingAB±79
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1
NG
OK
(1) Turn ignition switch LOCK, and wait at least 20
seconds.
(2) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(3) Repeat operation in step (1) and (2) at least 5 times.
(4) Using SST, connect terminals Tc and E
1 of TDCL.
SST 09843±18020
(5) Check diagnostic code.
Is diagnostic code 31 output again?
Using simulation method, reproduce
malfunction symptoms (See page IN±20).
Clear malfunction code stored in memory
(See page
AB±32).
Replace center airbag sensor assembly.
INSPECTION PROCEDURE
HINT:When a malfunction code other than code 31 is displayed at the same time, fi\
rst repair the malfunction indicated by the malfunction code other than code 31.
±
SRS AIRBAG TroubleshootingAB±81
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Clear malfunction code 41 stored in memory
(See page AB±32).
Check operation of airbag warning light.
NG
OK
1
Airbag warning light turns off.
(1) Turn ignition switch LOCK, and wait at least
2 seconds.
(2) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(3) Check operation of airbag warning light.
System is normal.
2Is diagnostic code 41 output again?
(1) Turn ignition switch ACC or ON, and wait at least 20 seconds.
(2) Using SST, connect terminals Tc and E
1 of TDCL.
SST 09843±18020
(3) Check diagnostic code.
Check harness between ECU±B fuse and center
airbag sensor assembly. If normal, replace
center airbag sensor assembly.
Perform troubleshooting according to malfunction code output.
NG
OK
INSPECTION PROCEDURE
±
SRS AIRBAG TroubleshootingAB±83
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