LEXUS SC400 1991 Service Repair Manual

BR±150). BE±163
.
IN±33
).
WIRING DIAGRAM
TRAC Indicator Light Circuit
CIRCUIT DESCRIPTION
The TRAC indicator blinks during TRAC operation.
This indicator is also used for warnings when the trouble occurs and for disp\
laying diagnostic trouble codes.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±225
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BR±160).
IN±33 ).
WIRING DIAGRAM
Tc Terminal Circuit
CIRCUIT DESCRIPTION
By connecting between terminals Tc and E1 of DLC1 or DLC2, the ECU displays the diagnostic trouble
code by blinking the TRAC indicator light.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±226±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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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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Check for Fluid Leakage
BR±228±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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SERVICE SPECIFICATIONS
SERVICE DATA
BR03A±0G\
\
Brake pedal height from asphalt sheet (LHD)  150.4±160.4 mm (5.92±6.31 in.)
\


\
Brake pedal freeplay 




1±6 mm (0.04±0.24 in.)
\


\
Brake pedal reserve distance at 490 N (50 kgf, 110.2
lbf) 





More than 89 mm (3.50 in.)
\
\
Brake booster push rod to piston clearance (w/ SST)  0 mm (0 in.)
\
\
Front brake pad thickness STD 11.0 mm (0.433 in.)
\
\
Front brake pad thickness Limit 1.0 mm (0.039 in.)\


\
Front brake disc thickness (SC 300)
 


STD


28.0 mm (1.102 in.)
\
\
Front brake disc thickness (SC 300) Limit 26.0 mm (1.024 in.)
\
\
Front brake disc thickness (SC 400) STD 32.0 mm (1.260 in.)
\


\
Front brake disc thickness (SC 400) 


Limit

30.0 mm (1.181 in.)
\
\
Front brake disc runout Limit 0.05 mm (0.0020 in.)
\
\
Rear brake disc pad thickness STD 10.0 mm (0.394 in.)
\
\
Rear brake disc pad thickness Limit 1.0 mm (0.039 in.)\


\
Rear brake disc thickness
 


STD


16.0 mm (0.630 in.)
\
\
Rear brake disc thickness Limit 15.0 mm (0.591 in.)
\
\
Rear brake disc runout Limit 0.05 mm (0.0020 in.)
\


\
Rear brake disc inside diameter 


STD

190 mm (7.48 in.)
\
\
Rear brake disc inside diameter Limit 191 mm (7.52 in.)
\
\
Parking brake lining thickness STD 2.5 mm (0.098 in.)
\
\
Parking brake lining thickness Limit 1.0 mm (0.039 in.)\


\
Parking brake lever travel at 196 N (20 kgf, 44.1 lbf)
 




5±8 clicks
\
\
Parking brake clearance between rear shoe and lever  Less than 0.35 mm (0.012 in.)
\


\
Parking brake adjusting shim thickness for rear disc
brake 




0.3 mm (0.012 in.)
\
\
  0.6 mm (0.024 in.)
\


\
 




0.9 mm (0.035 in.)
±
BRAKE SYSTEM SERVICE SPECIFICATIONSBR±229
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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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BRAKE SYSTEM
BR±1
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GENERAL DESCRIPTION
BR03E±06
1. Care must be taken to replace each part properly as it could affect the \
performance of the brakesystem and result in a driving hazard. Replace the parts with parts of the same part number or
equivalent.
2. It is very important to keep parts and the area clean when repairing the\
brake system.
3. If the vehicle is equipped with a mobile communication system, refer to the precaution \
in the IN section.
DESCRIPTION
BR03F±03
The service brakes consist of a foot brake which changes rotational energy to therma\
l energy to stop the
vehicle while it is being driven and a parking brake to keep the vehicle from m\
oving while it is parked.
OPERATION
FOOT BRAKE
BR03G±06
When the brake pedal is depressed, a vacuum builds up in the booster whi\
ch amplifies the pedal force,
pressing on the piston in the master cylinder. The piston movement raises the hydraulic pressure in the
cylinder. This hydraulic pressure is then applied to each respective brake cylin\
der, and acts to press the
brake pads against the rotating discs. The resulting friction converts the ro\
tational energy to thermal ener-
gy, stopping the vehicle.
BR±2±
BRAKE SYSTEM OPERATION
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GENERAL DESCRIPTION
BR03E±06
1. Care must be taken to replace each part properly as it could affect the \
performance of the brakesystem and result in a driving hazard. Replace the parts with parts of the same part number or
equivalent.
2. It is very important to keep parts and the area clean when repairing the\
brake system.
3. If the vehicle is equipped with a mobile communication system, refer to the precaution \
in the IN section.
DESCRIPTION
BR03F±03
The service brakes consist of a foot brake which changes rotational energy to therma\
l energy to stop the
vehicle while it is being driven and a parking brake to keep the vehicle from m\
oving while it is parked.
OPERATION
FOOT BRAKE
BR03G±06
When the brake pedal is depressed, a vacuum builds up in the booster whi\
ch amplifies the pedal force,
pressing on the piston in the master cylinder. The piston movement raises the hydraulic pressure in the
cylinder. This hydraulic pressure is then applied to each respective brake cylin\
der, and acts to press the
brake pads against the rotating discs. The resulting friction converts the ro\
tational energy to thermal ener-
gy, stopping the vehicle.
BR±2±
BRAKE SYSTEM OPERATION
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PARKING BRAKE
BR03H±04
When the parking brake lever is pulled up, the parking brake shoe lever is p\
ulled via the parking brake wire.
This causes the shoe strut to push the front shoe, which expands and is pres\
sed against the disc. If the
parking brake lever continues to be pulled up, the contact point of the parking\
brake shoe lever and shoe
strut then becomes the fulcrum so that the parking brake shoe lever causes th\
e rear shoe to expand. This
results in the disc being locked by the front shoe and rear shoe.
±
BRAKE SYSTEM OPERATIONBR±3
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