1991 LEXUS SC400 brake

TRAC ECU:
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±157
WhereEverybodyKnowsYourName

ECU TERMINALS STANDARD VALUE
ABS & TRAC ECU:
BR0F8±03
 Symbols
(Terminals No.) STD Voltage (V)\
 \
Condition
 

BAT
(A25±21)
 

±
 

GND
(A25±22)
 

10±14
\
 
\

\
Always
 

IG
(A24±24) 

±
 

GND
(A25±22) 

10±14
\
 
\

\
IG switch ON
 

SR
(A24±22) 

±
 

R±
(A24±25) 

8.3±14
\
 
\

\
IG switch ON, ABS warning light OFF
 


MR
(A25±16) 

± 


R±
(A24±25) 

Below 1.0\
 
\

\
IG switch ON
 


TSR
(A24±1) 

± 


R±
(A24±25) 

8.3±14\
 
\

\
IG switch ON, TRAC indicator light OFF
 


TMR
(A24±9) 


± 


R±
(A24±25) 


Below 1.0\
 
\

\

IG switch ON
 SFR
(A25±1) ± GND
(A25±2) 10±14\
 \
IG switch ON, ABS warning light OFF
 

SFL
(A24±13) 

±
 

GND
(A25±22) 

10±14
\
 
\

\
IG switch ON, ABS warning light OFF
 

SRR
(A24±26) 

±
 

GND
(A25±22) 

10±14
\
 
\

\
IG switch ON, ABS warning light OFF
 


SRL
(A25±12) 

±
 


GND
(A25±13) 

10±14
\
 
\

\
IG switch ON, ABS warning light OFF
 


AST
(A24±8) 

± 


GND
(A25±22) 

10±14\
 
\

\
IG switch ON, ABS warning light OFF
 


SAC
(A24±12) 


± 


GND
(A25±22) 


10±14\
 
\

\

IG switch ON, TRAC indicator light OFF
 SMC
(A24±2) ± GND
(A25±22) 10±14\
 \
IG switch ON, TRAC indicator light OFF
 

SRC
(A24±15)
 

±
 

GND
(A25±22
 

10±14
\
 
\

\
IG switch ON, TRAC indicator light OFF
 

PR
(A24±10) 

±
 

E2
(A24±20) 

5±7
\
 
\

\
IG switch ON
 


VC
(A24±19) 

±
 


E2
(A24±20) 

4±6
\
 
\

\
IG switch ON
 ALT 
±
 GND Below 1.0\
 \
IG switch ON
 ALT
(A25±8) ± GND
(A25±22) 10±14\
 \
Idling
 
WA
 
±
 
GND
 Below 2.0\
 \
IG switch ON, ABS warning light ON WA
(A25±9) ± GND
(A25±22) 10±14\
 \
IG switch ON, ABS warning light OFF 


PKB
 


±
 


GND
 

Below 1.5
\
 
\

\
IG switch ON, PKB switch ON,
Fluid in M/C reservoir above MIN level
 


PKB
(A25±17) 


± 


GND
(A25±22) 

10±14
\
 
\

\
IG switch ON, PKB switch OFF,
Fluid in M/C reservoir above MIN level
BR±158±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
WhereEverybodyKnowsYourName

 



Symbols
(Terminals No.) 


STD Voltage (V)\
 
\

\

Condition
 LBL
(A25±6)  ± GND
(A25±22) 10±14\
 \
IG switch ON
Fluid in M/C reservoir tank above MIN level.
 

STP
 

±
 

GND
 

Below 1.5\
 
\

\
Stop light switch OFF 


STP
(A25±10) 
± 


GND
(A25±22) 

8±14
\
 
\

\
Stop light switch ON
 D/G
(A25±20) ± GND
(A25±22) 10±14\
 \
IG switch ON, ABS warning light OFF
 

Tc
(A26±3)
 

±
 

GND
(A25±22)
 

10±14
\
 
\

\
IG switch ON
 

Ts
(A26±1) 

±
 

GND
(A25±22) 

10±14
\
 
\

\
IG switch ON
 P 
±
 GND 10±14\
 \
IG switch ON, Shift position in ªPº position P
(A26±10) ± GND
(A25±22) Below 1.5\
 \
IG switch ON, Other shift position in ªPº position 

N
 

±
 

GND
 

10±14\
 
\

\
IG switch ON, Shift position in ªNº position
 
N
(A26±5) 
±
 
GND
(A25±22) Below 1.5\
 \
IG switch ON, Other shift position in ªNº position
 

FR+
(A24±17) ± 

FR±
(A24±4) 

AC generation\
 
\

IG switch ON
Slowly turn right front wheel.
 

FL+
(A24±5)
 

±
 

FL±
(A24±18)
 

AC generation
\
 
\

\
IG switch ON
Slowly turn left front wheel.
 

RR+
(A25±14) 

±
 

RR±
(A25±3) 

AC generation
\
 
\

\
IG switch ON
Slowly turn right rear wheel.
 

RL+
(A25±4) 

±
 

RL±
(A25±15) 

AC generation
\
 
\

\
IG switch ON
Slowly turn left rear wheel.
 


FRO
(A26±15) 
± 


GND
(A25±22) 

Pulse generation\
 
\

\

IG switch ON
Slowly turn right front wheel.
 


FLO
(A26±6) 
± 


GND
(A25±22) 

Pulse generation\
 
\

\

IG switch ON
Slowly turn left front wheel.
 


RRO
(A26±13) 
± 


GND
(A25±22) 


Pulse generation\
 
\

\

IG switch ON
Slowly turn right rear wheel.
 RLO
(A26±4) ± GND
(A25±22) Pulse generation\
 \
IG switch ON
Slowly turn left rear wheel.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±159
WhereEverybodyKnowsYourName

TRAC ECU:
 

Symbols
(Terminals No.) 

STD Voltage (V)
\
 
\

\
Condition
 

BAT
(T13±8) 

±
 

GND
(T14±14) 

10±14
\
 
\

\
Always
 


BM
(T14±15) 
± 


GND
(T14±14) 

10±14\
 
\

\
Always
 


IG
(T14±2) 
± 


GND
(T14±14) 

10±14\
 
\

\
IG switch ON
 


ACM
(T14±13) 
± 


GND
(T14±14) 


4±5\
 
\

\

IG switch ON
Sub throttle valve fully open
 A
(T14±11) ± GND
(T14±14) 4±5\
 \
IG switch ON
Sub throttle valve fully open
 

A
(T14±12) 

±
 

GND
(T14±14) 

4±5
\
 
\

\
IG switch ON
Sub throttle valve fully open
 

BCM
(T14±26) 

±
 

GND
(T14±14) 

4±5
\
 
\

\
IG switch ON
Sub throttle valve fully open
 


B
(T14±24) 

±
 


GND
(T14±14) 

4±5
\
 
\

\

IG switch ON
Sub throttle valve fully open
 


B
(T14±25) 
± 


GND
(T14±14) 

4±5\
 
\

\

IG switch ON
Sub throttle valve fully open
 TR5 ± E1 Below 1.0\
 \
IG switch ON, Engine stopped
 
TR5
(T14±16) ± 
E1
(T14±20) 10±14\
 \
Engine idling
 IDL1 
±
 E1 Below 1.0\
 \
Engine idling, Main throttle valve fully closed
 IDL1
(T14±10) ± E1
(T14±20) 10±14\
 \
Engine idling, Main throttle valve fully open 
IDL2
 
±
 
E1
 Below 1.0\
 \
IG switch ON, Sub±throttle valve fully closed 


IDL2
(T14±22) 
± 


E1
(T14±20) 

10±14\
 
\

\
IG switch ON, Sub±throttle valve fully open
 VTH ± E1 Below 1.5\
 \
IG switch ON, Main throttle valve fully closed
 
VTH
(T14±8) 
±
 
E1
(T14±20) 3.0±5.5\
 \
IG switch ON, Main throttle valve fully open
 VSH ± E1 Below 1.5\
 \
IG switch ON, Sub±throttle valve fully closed
 
VSH
(T14±19) ± 
E1
(T14±20) 3.0±5.5\
 \
IG switch ON, Sub±throttle valve fully open
 


TR2
(T14±21) 
± 


E1
(T14±20) 

10±14\
 
\

\
IG switch ON
 


NEO
(T14±6) 
± 


E1
(T14±20) 

Pulse generation\
 
\

\
Engine idling
 CSW ± GND Below 1.5\
 \
IG switch ON, TRAC cut switch pushed in
 
CSW
(T13±13)  ± 
GND
(T14±14) 10±14\
 \
IG switch ON, TRAC cut switch released
    
Below 1 5
\
 \
IG switch ON, PKB switch ON,
 PKB 
±
 GND
(T14±14)
 Below 1.5\
 \
Fluid in M/C reservoir above MIN level
 PKB
(T14±1) ± (T14±14) 
10±14
\
 \
IG switch ON, PKB switch OFF,    10±14\
 \
Fluid M/C reservoir above MIN level
BR±160±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
WhereEverybodyKnowsYourName

 



Symbols
(Terminals No.) 


STD Voltage (V)\
 
\

\

Condition
 IND
(T13±11) ± GND
(T14±14) 10±14\
 \
IG switch ON, TRAC indicator light OFF
 

WT
 

±
 

GND
 

Below 2.0\
 
\

\
IG switch ON, TRAC OFF indicator light ON 


WT
(T13±14) 
± 


GND
(T14±14) 

10±14
\
 
\

\
IG switch ON, TRAC OFF indicator light OFF
 STP ± GND Below 1.5\
 \
Stop light switch OFF
 
STP
(T13±2) ± 
GND
(T14±14) 8±14\
 \
Stop light switch ON
 P 
±
 GND 10±14\
 \
IG switch ON, Shift position in ªPº position
 
P
(T13±7) ± 
GND
(T14±14) Below 1.5\
 \
IG switch ON, Other shift position in ªPº position
 N 
±
 GND 10±14\
 \
IG switch ON, Shift position in ªNº position
 N
(T13±16) ± GND
(T14±14) Below 1.5\
 \
IG switch ON, Other shift position in ªNº position 

Tc
(T13±6) 

±
 

GND
(T14±14) 

10±14
\
 
\

\
IG switch ON
 

FRO
(T13±10) 

±
 

GND
(T14±14) 

Pulse generation
\
 
\

\
IG switch ON
Slowly turn right front wheel
 


FLO
(T13±3) 
± 


GND
(T14±14) 

Pulse generation\
 
\

\

IG switch ON
Slowly turn left front wheel
 


RRO
(T13±12) 
± 


GND
(T14±14) 

Pulse generation\
 
\

\

IG switch ON
Slowly turn right rear wheel
 


RLO
(T13±5) 
± 


GND
(T14±14) 


Pulse generation\
 
\

\

IG switch ON
Slowly turn left rear wheel
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±161
WhereEverybodyKnowsYourName

ABBREVIATIONS USED IN THIS MANUAL
For convenience, the following abbreviations are used in this
manual.
ABS Antilock Brake System
assy assembly
ECT Electronic Controlled Transmission
ECU Electronic Control Unit
e.g. Exempi Gratia (For Example)
Ex. Except
in. inch
LH Left-hand
MIG Metal Inert Gas
M/Y Model Year
PPS Progressive Power Steering
RH Right-hand
w/ with
w/o without
INTRODUCTIONIN-16
WhereEverybodyKnowsYourName

CodeMaterial
name Heat *
resistant
temperature
limit
°C (°F) Resistance to
alcohol or gasoline Notes
AAS Acrylonitrile
Acrylic Styrene 80
(176) Alcohol is harmless if applied
only for short time in small
amounts (e.g., quick wiping to
remove grease). Avoid gasoline and or-
ganic or aromatic sol-
vents.
ABS Acrylonitrile
Butadiene Styrene 80
(176) Alcohol is harmless if applied
only for short time in small
amounts (e.g., quick wiping to
remove grease).
Avoid gasoline and or-
ganic or aromatic sol-
vents.
AES Acrylonitrile
Ethylene Styrene 80
(176) Alcohol is harmless if applied
only for short time in small
amounts (e.g., quick wiping to
remove grease). Avoid gasoline and or-
ganic or aromatic sol-
vents.
BMC Bulk
Moulding
Compound
150
(302) Alcohol and gasoline are
harmless. Most solvents are
harmless.
CAB Cellulose
Acetate 80
(176) Alcohol is harmless if applied
only for short time in small
amounts (e.g., quick wiping to
remove grease). Avoid gasoline and or-
ganic or aromatic sol-
vents.
EPDM Ethylene
Propylene 100
(212) Alcohol is harmless.
Gasoline is harmless if applied
only for short time in small
amounts. Most solvents are harm-
less but avoid dipping in
gasoline, solvents, etc.
PA Polyamide
(Nylon) 80
(176) Alcohol and gasoline are
harmless.
Avoid battery acid.
PBT Polybutylene
Terephthalate 160
(320) Alcohol and gasoline are
harmless. Most solvents are
harmless.
PC Polycarbonate 120
(248) Alcohol is harmless. Avoid gasoline, brake
fluid, wax, wax removers
and organic solvents.
PE Polyethylene 80
(176) Alcohol and gasoline are
harmless. Most solvents are
harmless.
PET Polyethylene
Terephthalate 75
(167) Alcohol and gasoline are
harmless.
Avoid dipping in water.
HANDLING PRECAUTIONS
1. The repair procedure for plastic body parts must conform with the type o\
f plastic material.
2. Plastic body parts are identified by the codes in the following chart.
3. When repairing metal body parts adjoining plastic body parts (by brazin\
g, frame cutting, welding, paint-
ing, etc.), consideration must given to the property of the plastic.
*Temperatures higher than those listed here may result in material deforma\
tion during repair.
PLASTIC BODY PARTSPP-2
WhereEverybodyKnowsYourName

Shift Lock ECU
Tilt and Power
Telescopic ECU
Airbag ECU
Cruise Control ECU Engine ECUABS and Traction ECU
(w/ Traction System) or
ABS ECU
(w/o Traction System)
Theft Deterrent and
Door Lock ECU
(w/ Traction System)
Traction ECU
Remote Control Mirror ECU A/C Control Amplifier
PPS ECU
Engine Cooling Fan ECU
Component to be aligned
Section of repair manual
for relevant model year
Front Wheels Suspension and Axle (SA) section
Rear Wheels Suspension and Axle (SA) section
Propeller Shaft Propeller Shaft (PR) section
2. BRAKE SYSTEM
The brake system is one of the most important safety components. Always \
follow the directions and
notes given in section BR of the repair manual for the relevant model ye\
ar when handling brake sys-
tem parts.
NOTICE: When repairing the brake master cylinder or TRAC system, bleed t\
he air out of the TRAC
system.
3. DRIVE TRAIN AND CHASSIS
The drive train and chassis are components that can have great effects on the running performance
and vibration resistance of the vehicle. After installing components in \
the sections listed in the table
below, perform alignments to ensure correct mounting angles and dimensions. P\
articularly accurate
repair of the body must also be done to ensure correct alignment.
HINT: Correct procedures and special tools are required for alignment. Alway\
s follow the directionsgiven in the repair manual for the relevant model year during alignment \
and section DI of this manual.
4. ECU (ELECTRONIC CONTROL UNIT)
Locations of ECUs
INTRODUCTIONIN-8
WhereEverybodyKnowsYourName