1991 LEXUS SC400 light

4. CHECK THAT PEDAL RESERVE DISTANCE IS CORRECT,
AS SHOWN
Release the parking brake.
With the engine running, depress the pedal and measure the
pedal reserve distance, as shown.
Pedal reserve distance at 490 N (50 kgf, 110.2 lbf):
More than 89 mm (3.50 in.)
If the reserve distance is incorrect, troubleshoot the brake
system.
BRAKE BOOSTER OPERATIONAL TEST
BR03P±0B
1. OPERATING CHECK
(a) Depress the bake pedal several times with the engine off and
check that there is no change in the pedal reserve distance.
(b) Depress the brake pedal and start the engine. If the pedal goes down slightly, operation is normal.
2. AIR TIGHTNESS CHECK
(a) Start the engine and stop it after 1 or 2 minutes. Depress the brake pedal several times slowly. If the pedal goes down the
farthest the 1st time, but gradually rises after the 2nd or 3rd
time, the booster is air tight.
(b) Depress the brake pedal while the engine is running, and stop the engine with the pedal depressed. If there is no
change in the pedal reserve travel after holding the pedal for
30 seconds, the booster is air tight.
BRAKE SYSTEM BLEEDING
BR0ED±04
HINT: If any work is done on the brake system or if air in the
brake lines is suspected, bleed the system of air.
NOTICE: Do not let brake fluid remain on painted sur-
faces. Wash it off immediately.
1. REMOVE RESERVOIR CAP Turn the reservoir cap to the ªopenº side and remove it.
2. FILL RESERVOIR WITH BRAKE FLUID
Fluid: SAE J1703 or FMVSS NO.116DOT3
BR±8±
BRAKE SYSTEM CHECK AND ADJUSTMENT
WhereEverybodyKnowsYourName

3. REMOVE RESERVOIRRemove the set screw and pull out the reservoir.
4. REMOVE 2 GROMMETS
5. PLACE CYLINDER IN VISE
6. w/ TRAC: REMOVE NO.1 PISTON STOPPER BOLT
Using a screwdriver, push the pistons in all the way and re-
move the No.1 piston stopper bolt and gasket.
HINT: Tape the screwdriver tip before use.
7. REMOVE NO.2 PISTON STOPPER BOLT Using a screwdriver, push the pistons in all the way and re-
move the No.2 piston stopper bolt and gasket.
8. REMOVE PISTONS
(a) Push in the piston with a screwdriver and remove the snap ring with snap ring pliers.
(b) Remove the No. 1 piston and spring by hand, pulling straight out, not at an angle.
NOTICE: If pulled out at an angle, there is a possibility that the
cylinder bore could be damaged.
(c) Place a rag and 2 wooden blocks on the work table and lightly
tap the cylinder flange against the block edges until the piston
drops out of the cylinder.
HINT: Make sure the distance (A) from the rag to the top of
the blocks is at least 100 mm (3.94 in.).
MASTER CYLINDER COMPONENTS
INSPECTION
BR03V±05
HINT: Clean the disassembled parts with compressed air.
1. INSPECT CYLINDER BORE FOR RUST OR SCORING
2. INSPECT CYLINDER FOR WEAR OR DAMAGE If necessary, clean or replace the cylinder.
±
BRAKE SYSTEM MASTER CYLINDERBR±15
WhereEverybodyKnowsYourName

3. REMOVE BRAKE BOOSTER
(a) Remove the booster installation nuts.
(b) Remove the booster and gasket.
BRAKE BOOSTER INSTALLATION
BR03Z±08
1. INSTALL BRAKE BOOSTER
(a) Install the booster and gasket.
(b) Install and torque the booster installation nuts.
Torque: 12 NVm (125 kgf Vcm, 9 ft Vlbf)
(c) Insert the clevis pin into the clevis and brake pedal, and install
the clip to the clevis pin.
(d) Install the pedal return spring.
2. ADJUST LENGTH OF BOOSTER PUSH ROD
(a) Install the gasket on the master cylinder.
(b) Set the SST on the gasket, and lower the pin until its tip slightly touches the piston.
SST 09737±00010
(c) Turn the SST upside down, and set it on the booster. SST 09737±00010
(d) Measure the clearance between the booster push rod and
pin head (SST).
Clearance:
0 mm (0 in.)
(e) Adjust the booster push rod length until the push rod lightlytouches the pin head.
HINT: When adjusting the push rod, depress the brake pedal
enough so that the push rod sticks out.
3. INSTALL FOLLOWING PARTS: wVacuum hose
w Master cylinder
(See page BR±12)
w w/ TRAC:
TRAC pump assembly
(See page BR±162)
±
BRAKE SYSTEM BRAKE BOOSTERBR±19
WhereEverybodyKnowsYourName

BR0EY±05
ECU TERMINALS STANDARD VALUE
w/o TRAC:
 


Symbols
(Terminals No.) 

STD Voltage (V)\
 
\

\
Condition
 


BAT
(A23±22) 
± 


GND
(A23±13) 


10±14\
 
\

\

Always
 IG
(A23±11) ± GND
(A23±2) 10±14\
 \
IG switch ON
 

SR
(A22±5) 

±
 

R±
(A22±4) 

8.3±14
\
 
\

\
IG switch ON, ABS warning light OFF
 

MR
(A22±11) 

±
 

R±
(A22±4) 

Below 1.0
\
 
\

\
IG switch ON
 


SFR
(A23±1) 

±
 


GND
(A23±2) 

10±14
\
 
\

\
IG switch ON, ABS warning light OFF
 


SFL
(A22±6) 
± 


GND
(A23±13) 

10±14\
 
\

\
IG switch ON, ABS warning light OFF
 


SRR
(A22±12) 
± 


GND
(A23±13) 

10±14\
 
\

\
IG switch ON, ABS warning light OFF
 AST
(A22±8) ± GND
(A23±13) 10±14\
 \
IG switch ON, ABS warning light OFF
 

WA
 

±
 

GND
 

Below 2.0
\
 
\

\
IG switch ON, ABS warning light ON
 
WA
(A23±10) 
±
 
GND
(A23±13) 10±14\
 \
IG switch ON, ABS warning light OFF
 PKB ± GND Below 1.5\
 \
IG switch ON, PKB switch ON
 
PKB
(A23±16) ± 
GND
(A23±13) 10±14\
 \
IG switch ON, PKB switch OFF
 STP 
±
 GND Below 1.5\
 \
Stop light switch OFF
 STP
(A23±7) ± GND
(A23±2) 8±14\
 \
Stop light switch ON
 

D/G
(A23±21) 

±
 

GND
(A23±13) 

10±14
\
 
\

\
IG switch ON, ABS warning light OFF
 


Tc
(A23±17) 

±
 


GND
(A23±13) 

10±14
\
 
\

\
IG switch ON
 


Ts
(A23±6) 
± 


GND
(A23±2) 

10±14\
 
\

\
IG switch ON
 


FR+
(A22±1) 
± 


FR±
(A22±7) 


AC generation\
 
\

\

IG switch ON
Slowly turn right front wheel
 FL+
(A22±3) ± FL±
(A22±10) AC generation\
 \
IG switch ON
Slowly turn left front wheel
 

RR+
(A23±19)
 

±
 

RR±
(A23±20)
 

AC generation
\
 
\

\
IG switch ON
Slowly turn right rear wheel
 

RL+
(A23±14) 

±
 

RL±
(A23±3) 

AC generation
\
 
\

\
IG switch ON
Slowly turn left rear wheel
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±59
WhereEverybodyKnowsYourName

w/TRAC:
 


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) 

Below1.0
\
 
\

\
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±60±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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
(A25±22)
 

10±14
\
 
\

\
IG switch ON, Shift position in ªNº position
 
N
(A26±5) ± (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 ANTI±LOCK BRAKE SYSTEM (ABS)BR±61
WhereEverybodyKnowsYourName

MAIN POINT OF REMOVAL AND
INSTALLATION
1. w/ TRAC:DRAIN OUT HIGH PRESSURE FLUID
(a) Connect a vinyl t ube to the TRAC actuator bleeder plug, then
loosen the bleeder plug.
(b) When the fluid has flowed out, tighten the bleeder plug. CAUTION: Since the fluid is under high pressure, it could
stray out with great force, so be careful.
2. DISCONNECT AND CONNECT BRAKE LINE w/ TRAC:
Using SST, disconnect and connect the brake lines from/to
the ABS actuator and TRAC actuator.
SST 09023±00100
Torque: 15 N Vm (155 kgf Vcm, 11 ft Vlbf)
w/o TRAC:
Using SST, disconnect and connect the brake lines from/to
the ABS actuator.
SST 09023±00100
Torque: 15 N Vm (155 kgf Vcm, 11 ft Vlbf)
3. w/ TRAC:
REMOVE AND INSTALL TRAC ACTUATOR
Loosen and tighten the 3 bolts.
Torque: 15 N Vm (155 kgf Vcm, 11 ft Vlbf)
HINT: When loosening or tightening TRAC actuator installa-
tion bolts, lift the actuator bracket up slightly from the body.
4. BLEED BRAKE SYSTEM
(See page BR±8)
5. w/ TRAC: BLEED TRAC SYSTEM
(See page BR±10)
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±63
WhereEverybodyKnowsYourName

TROUBLESHOOTING
How to proceed with troubleshooting
Perform troubleshooting in accordance with the procedure on the followin\
g pages.

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 ABS warning light lights up, and the ABS does not operate, the ECU \
stores diagnostic trouble codes
corresponding to the problem in memory.
Before confirming the trouble, 1st check the diagnostic trouble codes for any \
malfunction codes stored in
memory. When there are malfunction codes, make a note of them, then clear them \
and proceed to ª  Prob-
lem 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 indicted 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 are 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 ABS system is operating correctly. (In vehicles with the TRAC system, also check
the TRAC system.)
BR±72
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
WhereEverybodyKnowsYourName