abs system LEXUS SC300 1991 Service User Guide

(Vanity Light Switch)
REMOVAL AND INSTALLATION OF
VANITY LIGHT SWITCH
1. REMOVE VANITY LIGHT(a) Release two tabs and remove the lens.
(b) Remove two screws and separate the vanity light from sun visor.
(c) Disconnect connector and remove vanity light.
2. INSTALL VANITY LIGHT For installation follow the removal procedure in reverse.
INSPECTION OF VANITY LIGHT
INSPECT VANITY LIGHT SWITCH
(Continuity)
Inspect the vanity light continuity between terminals.
If continuity is not as specified, replace bulb or vanity light.
(Switch Circuit)
Disconnect the connector from the switch and inspect the
connector on the wire harness side as shown.
Check forTester connectionConditionSpecified value
Voltage1±GroundConstantBattery positive voltage
Continuity2±GroundConstantContinuity
If circuit is not as specified, inspect power source or wire har-
ness.
±
BODY ELECTRICAL SYSTEM Lighting SystemBE±81
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TROUBLESHOOTING
How to proceed with troubleshooting
Perform troubleshooting in accordance with the procedure on the followin\
g page.

CUSTOMER PROBLEM ANALYSIS
Using the customer problem analysis check sheet for reference, ask the c\
ustomer in as much detail as
possible about the problem.
CHECK AND CLEAR THE DIAGNOSTIC TROUBLE CODES (PRECHECK)
If the TRAC indicator light lights up, and the TRAC control does not ope\
rate, the ECU stores diagnostic
trouble codes corresponding to the problem in memory.
Before confirming the trouble, first check the diagnostic trouble code for any\
malfunction codes stored in
memory. When there are malfunction codes, make a note of them, then clear them and proceed to ª 
Problem Symptom Confirmationº.
 PROBLEM SYMPTOM CONFIRMATION,  SYMPTOM SIMULATION
Confirm the problem symptoms. If the problem does not reoccur, simulate the problem by initially checking
the circuits indicated by the diagnostic trouble code in step , using ªProblem simulation methodº.
 DIAGNOSTIC TROUBLE CODE CHECK
Check the diagnostic trouble codes. If a malfunction code is output, proceed \
to ª  Diagnostic Trouble
Code Chartº.
If the normal code is output, proceed to ª  Problem Symptoms Chartº.
Be sure to proceed to ª  diagnostic Trouble Code Chartº after steps and  are completed.
If troubleshooting is attempted only by following the malfunction code sto\
red in the memory, errors could
be made in the diagnosis.
 DIAGNOSTIC TROUBLE CODE CHART
If a malfunction code is confirmed in the diagnostic trouble code check,\
proceed to the inspection proce-
dure indicated by the matrix chart for each diagnostic trouble code.
 PROBLEM SYMPTOMS CHART
If the normal code is confirmed in the diagnostic trouble code check, perf\
orm inspection in accordance with
the inspection order in the problem symptoms chart.
 CIRCUIT INSPECTION
Proceed with diagnosis of each circuit in accordance with the inspection\
order confirmed in  and .
Determine whether the cause of the problem is in the sensor, actuators, wire harness and connectors or
the ECU.
\b SENSOR CHECK
Use the ABS warning light to check if each of the signals from speed sensors is \
being input correctly to
the ECU. Instructions for this check are given in the circuit inspection\
.
[10] REPAIRS After the cause of the problem is located, perform repairs by following the i\
nspection and replacement pro-
cedures in this manual.
[11] CONFIRMATION TEST
After completing repairs, confirm not only that the malfunction is eliminated\
, but also conduct a test drive
to make sure the entire TRAC system is operating correctly. And also check the ABS is operating correctly.
BR±166
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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DIAGNOSTIC TROUBLE CODE CHART
If a malfunction code is displayed during the diagnostic trouble code chec\
k, check the circuit listed for that code
in the table below and proceed to the page given.
HINT: If the TRAC indicator light lights up and the TRAC indicator light doe\
s not blink when the Diag. code is
checked, check the blinking pattern of the ABS warning light and perform trouble\
shooting of the ABS system.
BR±186BR±189
BR±190
BR±192
BR±196 BR±198
BR±200
BR±208
BR±216
BR±218
BR±220BR±189
BR±189
BR±190
BR±190
BR±190
BR±200 BR±208
*1: If a malfunction is detected, the TRAC OFF indicator light lights up.
*2: Indicator light does not lights up even if an error is detected.
*3: If a malfunction is detected, the TRAC OFF indicator light or TRAC i\
ndicator light light up.
BR±172
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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The speed sensor detects the wheel speed and sends the ap-
propriate signals to the ECU. These signals are used for control
of both the ABS and TRAC control systems. The front and rear
rotors each have 48 serrations. When the rotors rotate, the mag-
netic field emitted by the permanent magnet in the speed sensor
generates an AC voltage. Since the frequency of this AC voltage
changes in proportion to the speed of the rotors (wheels), the
frequency is used by the ECU to detect the speed of each wheel.
BR3583
BR3582
DTC31, 32,
33, 34Speed Sensor Circuit
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
31, 32,
33, 34
Detection of any of conditions (1) through (3):
(1) At vehicle speed of 10 km/h (6 mph) or more, pulses are not input for 5 sec.
(2) Momentary interruption of the vehicle speed sen- sor signal occurs at least 7 times in the time be-
tween switching the ignition switch ON and switch-
ing it OFF.
(3) Abnormal fluctuation of speed sensor signals with the vehicle speed 20 km/h (12 mph) or more.

Right front, left front, right rear and left rear
speed sensor.

Open or short in each speed sensor circuit.

ECU
Hint: DTC No. 31 is for the right front wheel speed sensor.
DTC No. 32 is for the left front wheel speed sensor.
DTC No. 33 is for the right rear wheel speed sensor.
DTC No. 34 is for the left rear wheel speed sensor.
Fail safe function: If trouble occurs in the speed sensor circuit, the E\
CU prohibits TRAC control.
BR±190
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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WIRING DIAGRAM
DTC43ABS & TRAC ECU Malfunction
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
43ABS control system or TRAC (BRAKE) control system
or communication circuit is abnormal.
ABS & TRAC ECU

Open or short in BRFA circuit
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±196±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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NGOK
NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminal BRFA of TRAC ECU and body ground.
C
OK
P1. Remove TRAC ECU with connectors still con-nected.
2. Turn ignition switch ON.
Measure voltage between terminal BRFA of TRAC ECU
and body ground.
Voltage: About 6 V (Pulse)
Check and replace TRAC ECU.
2Check voltage between terminal BRFA of TRAC ECU and body ground with TRAC ECU connec-
tor is disconnected.
C
OK
Hint
PDisconnect TRAC ECU connector.
Measure voltage between terminal BRFA of TRAC ECU
connector and body ground.
Measure voltage within 8 seconds from the time TRAC
ECU connector is disconnected.
Voltage: See step 1.
Check and replace TRAC ECU.
3Check for open and short in harness and connector between ABS & TRAC ECU and TRAC ECU
(See page IN±33).
Repair or replace harness or connector.
Check and replace ABS & TRAC ECU.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±197
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WIRING DIAGRAM
DTC61ABS & TRAC ECU Communication Circuit
Malfunction
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
61Malfunction in ABS & TRAC ECU communication cir-
cuit.
Open or short in ABSO, BRC, BRP circuit

ABS & TRAC ECU

TRAC ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±220±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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OKNG
NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals ABSO, BRC, BRP of TRAC ECU and body ground.
C
OK
Hint
PRemove TRAC ECU with connectors still connected.
Measure voltage between terminals ABSO, BRC, BRP
of TRAC ECU and body ground when ignition switch is
turned ON.
Voltage: ABSO, BRC: 6 ± 14 VBRP: About 7 V (Pulse)\
(Reference)
Check and replace TRAC ECU.
2Check voltage between terminals ABSO, BRC, BRP or TRAC ECU and body ground wi\
th TRAC
ECU connector is disconnected.
C
OK
Hint
PDisconnect TRAC ECU connector.
Measure voltage between terminals ABSO, BRC, BRP
or TRAC ECU connector and body ground when ignition
switch is turned ON.
Voltage: See step 1.
Check and replace TRAC ECU.
3Check for open and short in harness and connector between ABS & TRAC ECU and TRAC ECU
(See page IN±33).
Repair or replace harness or connector.
Check and replace ABS & TRAC ECU.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±221
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NGOK
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals Tc and E1 of DLC 2 or DLC 1.
C
OK
PTurn ignition switch ON.
Measure voltage between terminals TC and E1 of DLC
2 or DLC 1.
Voltage: 10 ± 14 V
Proceed to next circuit inspection shown on problem
symptoms chart (See page BR±160).
2Check for open and short in harness and connector between ABS & TRAC ECU, TRAC\
ECU and
DLC 2 (or DLC 1), DLC 2 (or DLC 1) and body ground (See page IN±33).
Repair or replace harness or connector.
Check and replace TRAC ECU.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±227
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TORQUE SPECIFICATIONS
BR03B±0G\
 
\

\
Part tightened
 

N
Vm
 

kgf
Vcm
 

ft
Vlbf
\
 \
Master cylinder x Piston stopper bolts 10 100 7
\
 \
Master cylinder x Reservoir 1.7 17.5 15.2 in. Vlbf
\
 
\

\
Master cylinder x Brake booster 

13 

130 

9
\
 \
Brake tube union nut 15 155 11
\
 \
Brake booster clevis lock nut 25 260 19
\
 \
Brake booster x Pedal bracket 15 150 11\
 
\

\
Bleeder plug (TRAC actuator and TRAC accumulator)
 

8.3
 

85
 

74 in.
Vlbf
\
 \
Bleeder plug 11 11 0 8
\
 \
Front disc brake torque plate x Steering knuckle 11 8 1,200 87
\
 \
Front disc brake cylinder installation bolt 34 350 25\
 
\

\
Front disc brake cylinder x Flexible hose bolt
 

30
 

310
 

22
\
 \
Rear disc brake torque plate x Axle carrier 104 1,065 77
\
 \
Rear disc brake cylinder installation bolt 34 350 25
\
 
\

\
Rear disc brake x Flexible hose union bolt 

30 

310 

22
\
 \
Parking brake lever x Floor 59 600 43
\
 \
Parking brake cable No.1 x Floor 9 80 69 in.
Vlbf
\
 \
Parking brake cable retainer x Floor 5.4 55 48 in. Vlbf\
 
\

\
Parking brake cable clamp x Floor
 

19
 

190
 

14
\
 \
ABS actuator x Actuator bracket 5.4 55 48 in.
Vlbf
\
 \
ABS actuator bracket x Body 19 195 14
\
 
\

\
Front speed sensor installation bolt 

7.8 

80 

69 in.
Vlbf
\
 \
Rear speed sensor installation bolt 7.8 80 69 in. Vlbf
\
 \
TRAC pump bracket x Body 19 195 14
\
 \
TRAC pump or accumulator x Union bolt 46 465 34
BR±230±
BRAKE SYSTEM SERVICE SPECIFICATIONS
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