LEXUS SC400 1991 Service Repair Manual

Check for Fluid Leakage.
BR±152±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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TRACTION CONTROL SYSTEM (TRAC)
DESCRIPTION
BR0F3±01
The TRAC (Traction Control) system totally controls the engine torque and the braking of the driving wheels
(rear wheels). It helps avoid slippage of the driving wheels that tends to h\
appen during starting and accel-
eration and to maintain an optimal driving force according to the road surface conditions. The syst\
em elimi-
nates the need for a subtle accelerator pedal operation and improves veh\
icle stability when starting, accel-
erating or turning on slippery roads.
The TRAC system is an option.
SYSTEM PARTS LOCATION
BR0F4±01
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±153
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HYDRAULIC SYSTEM DIAGRAM
BR0F5±01
BR±154±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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WIRING DIAGRAM
BR0F6±01
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±155
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ECU TERMINALS
ABS & TRAC ECU:
BR0F7±05
BR±156±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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TRAC ECU:
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±157
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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
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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
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