abs system LEXUS SC300 1991 Service Repair Manual

Check for Fluid Leakage.
BR±152±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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ECU TERMINALS
ABS & TRAC ECU:
BR0F7±05
BR±156±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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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)
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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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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
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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
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FUEL EVAPORATIVE EMISSION CONTROL (EVAP) SYSTEM
DESCRIPTION
To reduce HC emission, evaporated fuel from the fuel tank is routed throug\
h the charcoal canister to the
intake manifold for combustion in the cylinders.
OPERATION
CoolantVSVThrottle ValveCanister Check ValveCheck
Valve inEvaporated F el (HC)Coolant
Te m p .VSVThrottle Valve
Opening(1)(2)(3)Valve inCapEvaporated Fuel (HC)
BelowNoFulley closedBelow
40 5C (104 5F)
No
OperationFulley closed.±±±±Small volume of HC from
Fully closed or
bellow Specified air
canister enters air intake
chamber.
Above
bellow Specified air
volume.±±±±chamber.
Above
40 5C (104 5F)Operation
Conditions other
than above.±±±±
HC from canister enters air
intake chamber in the amout
programmed in accordance
with the intake air volume.
High pres-
sure in tank±±±OPENCLOSEDCLOSEDHC from tank is absorbed
into the canister.
High vacuum
in tank±±±CLOSEDOPENOPENAir is led into the fuel tank.
INSPECTION OF FUEL VAPOR LINES,
FUEL TANK AND TANK CAP
1. VISUALLY INSPECT LINES AND CONNECTIONS
Look for loose connections, sharp bends or damage.
2. VISUALLY INSPECT FUEL TANK Look for deformation, cracks or fuel leakage.
EC±8
±
EMISSION CONTROL SYSTEMS Fuel Evaporative Emission Control (EVAP) System
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FUEL SYSTEM
Fuel is pumped up by the fuel pump, which flows through the fuel filter unde\
r pressure through the fuel pipe
to the delivery pipe where it is distributed to each injector. The fuel pressure regulator adjusts the pressure of the fuel from the fuel \
line (high pressure side) to a pressure
284 kPa (2.9 kgf/cm2, 41 psi) higher than the pressure inside the intake \
manifold, and excess fuel is returned
to the fuel tank through the return pipe.
When the engine is hot, the fuel pressure is increased to control percolation in the fuel system and impr\
ove
restartability and idling stability.
The pulsation damper absorbs the slight fluctuations in fuel pressure ca\
used by the injector.
The injectors operate on input of injection signals from the ECU and inj\
ect fuel into the intake manifold.
FI±6
±
EFI SYSTEM Operation
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FUEL SYSTEM
Fuel is pumped up by the fuel pump, which flows through the fuel filter under pr\
essure through the fuel pipe
to the delivery pipe where it is distributed to each injector and the cold\
start injector.
The fuel pressure regulator adjusts the pressure of the fuel from the fuel \
line (high pressure side) to a pres-
sure 284 kPa (2.9 kgf/cm
2, 41 psi) higher than the pressure inside the intake manifold, and exce\
ss fuel is re-
turned to the fuel tank through the return pipe.
When the engine is hot, the fuel pressure is increased to control percolatio\
n in the fuel system and improve
restartability and idling stability.
The pulsation damper absorbs the slight fluctuations in fuel pressure ca\
used by the injector.
The injectors operate on input of injection signals from the ECU and inj\
ect fuel into the intake manifold.
The cold start injector operates when starting with low coolant temperature or at normal temperature
ranges, injecting fuel into the air intake chamber to improve startability. FI±7
EFI SYSTEM
± Operation
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IF VEHICLE IS EQUIPPED WITH MOBILE
RADIO SYSTEM (HAM, CB, ETC.)
The ECU has been designed so that it will not be affected by out-
side interference. However, if your vehicle is equipped with a CB
radio transceiver, etc. (even one with about 10 W output), it may,
at times, have an effect upon ECU operation, especially if the an-
tenna and feeder are installed nearby.
Therefore, observe the following precautions:
1. Install the antenna as far away as possible from the ECU. The ECU is located on the floor panel on the passenger side
so the antenna should be installed at the rear of the vehicle.
2. Keep the antenna feeder as far away as possible from the ECU wires±at least 20 cm (7.87 in.) ±and, especially, do not
wind them together.
3. Check that the feeder and antenna are properly adjusted.
4. Do not equip your vehicle with a powerful mobile radio
system.
5. Do not open the cover or the case of the ECU unless absolutely necessary. (If the IC terminals are touched, the IC
may be destroyed by static electricity.)
AIR INDUCTION SYSTEM
1. Separation of the engine oil dipstick, oil filler cap, PCV hose,
etc. may cause the engine to run out of tune.
2. Disconnection, looseness or cracks in the parts of the air
induction system between the throttle body and cylinder
head will cause air suction and cause the engine to run out
of tune.
ELECTRONIC CONTROL SYSTEM
1. Before removing EFI wiring connectors, terminals, etc., firstdisconnect the power by either turning the ignition switch
OFF or disconnecting the battery terminals.
HINT: Always check the diagnosis code before disconnecting
the battery terminals.
2. When installing the battery, be especially careful not to
incorrectly connect the positive (+) and negative (±) cables.
3. Do not permit parts to receive a severe impact during removal or installation. Handle all EFI parts carefully, especially the
ECU.
4. Do not be careless during troubleshooting as there are numerous transistor circuits and even slight terminal contact
can cause further troubles.
5. Do not open the ECU cover.
6. When inspecting during rainy weather, take care to prevent entry of water. Also, when washing the engine compartment,
prevent water from getting on the EFI parts and wiring
connectors.
7. Parts should be replaced as an assembly.
FI±12
±
EFI SYSTEM Inspection Precautions
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