ABS LEXUS SC400 1991 Service Repair Manual

139
(FOR ABS)
THIS SYSTEM CONTROLS THE RESPECTIVE BRAKE FLUID PRESSURES ACTING ON THE DISC\
BRAKE CYLINDERS OF THE RIGHT
FRONT WHEEL, LEFT FRONT WHEEL AND REAR WHEELS WHEN THE BRAKES ARE APPLIED IN \
A PANIC STOP SO THAT THE
WHEELS DO NOT LOCK. THIS RESULTS IN IMPROVED DIRECTIONALLY STABILITY AND STEERABILITY DURING PANIC BRAKING.
1. INPUT SIGNALS
(1) SPEED SENSOR SIGNALTHE SPEED OF THE WHEELS IS DETECTED AND INPUT TO TERMINALS FL+, FR+, RL+ AND RR+ OF THE ABS AND TRACTION
ECU.
(2) STOP LIGHT SW SIGNAL A SIGNAL IS INPUT TO TERMINAL STP OF THE ABS AND TRACTION ECU WHEN THE BRAKE PEDAL IS OPERATED.
(3) PARKING BRAKE SW SIGNAL A SIGNAL IS INPUT TO TERMINAL PKB OF THE ABS AND TRACTION ECU WHEN THE PARKING BRAKE IS OPERATED.
2. SYSTEM OPERATION
DURING SUDDEN BRAKING, THE ABS AND TRACTION ECU WHICH HAS SIGNALS INPUT FROM E\
ACH SENSOR CONTROLS THE
CURRENT FLOWING TO THE SOLENOID INSIDE THE ACTUATOR AND LETS THE HYDRAULIC PRESSURE ACTING ON EACH WHEEL
CYLINDER ESCAPE TO THE RESERVOIR. THE PUMP INSIDE THE ACTUATOR IS ALSO OPERATING AT THIS TIME AND IT RETURNS
THE BRAKE FLUID FROM THE RESERVOIR TO THE MASTER CYLINDER, THUS PREVENTING LOCKING OF THE VEHICLE WHEELS.
IF THE ECU JUDGES THAT THE HYDRAULIC PRESSURE ACTING ON THE WHEEL CYLINDER IS INSUFFICIENT, THE CURRENT
ACTING ON SOLENOID IS CONTROLLED AND THE HYDRAULIC PRESSURE IS INCREASED, HOLD\
ING OF THE HYDRAULIC
PRESSURE IS ALSO CONTROLLED BY THE COMPUTER, BY THE SAME METHOD AS ABOVE. BY REP\
EATED PRESSURE REDUCTION,
HOLDING AND INCREASE ARE REPEATED TO MAINTAIN VEHICLE STABILITY AND TO IMPROVE STEERABILITY DURING SUDDEN
BRAKING.
(FOR TRACTION CONTROL)
THE TRACTION CONTROL SYSTEM IS A SYSTEM WHEREBY THE ªABS AND TRACTION ECUº AND ªTRACTION ECUº\
CONTROLS THE
ENGINE TORQUE AND THE HYDRAULIC PRESSURE OF THE WHEEL CYLINDER OF THE DRIVING WHEELS IN ORDER TO CONTROL
SPINNING OF THE DRIVING WHEELS WHEN STARTING OFF AND ACCELERATING, AND PROVIDE THE MOST APPROPRIATE DRIVING
FORCE IN RESPONSE TO THE ROAD CONDITIONS FOR VEHICLE STABILITY.
TRACTION CONTROL OPERATION
VEHICLE SPEED SIGNALS FROM THE SPEED SENSOR INSTALLED ON EACH WHEEL ARE INPUT TO THE ABS AND TRACTION ECU.
WHEN THE ACCELERATOR PEDAL IS DEPRESSED WHILE DRIVING ON A SLIPPERY ROAD AND THE DRIVING WHEEL (REAR WHEEL)
SLIPS, IF THE ROTATION OF THE REAR WHEEL EXCEEDS THE ROTATION OF THE FRONT WHEELS FOR A SPECIFIED PERIOD, THE
ECU JUDGES THAT THE REAR WHEEL IS SLIPPING.
WHEN THIS OCCURS, CURRENT FLOWS FROM TRACTION ECU TO SUB THROTTLE ACTUATOR TO CLOSE THE SUB THROTTLE
VALVE. THE THROTTLE VALVE OPENING ANGLE SIGNAL IS OUTPUT FROM TERMINAL VTA OF SUB THROTTLE POSITION SENSOR
TO TERMINAL VTA2 OF ENGINE AND ECT ECU TO KEEP THE ENGINE RPM AT THE MOST SUITABLE LEVEL FOR THE DRIVING
CONDITIONS AND REDUCE SLIP OF THE DRIVING WHEEL. AT THE SAME TIME, OPERATION OF THE ABS AND TRACTION ECU
CAUSE THE TRACTION BRAKE ACTUATORS (ACC CUT, M/C CUT, RESERVOIR CUT SOLENOID) TO TURN ON TO SWITCH THE
HYDRAULIC CIRCUIT TO ªTRACTIONº MODE.
IN THIS CASE, SIGNALS ARE INPUT FROM TERMINAL SRR OF ABS AND TRACTION ECU TO TERMINAL (B)6 OF ABS ACTUATOR, AND
FROM TERMINAL SRL OF ABS AND TRACTION ECU TO TERMINAL (B)1 OF ABS ACTUATOR, CONTROLLING THE REAR WHEEL
SOLENOID IN THE ABS ACTUATOR AND INCREASING THE HYDRAULIC PRESSURE OF THE WHEEL CYLINDER IN ORDER \
TO
PREVENT SLIP.
TO MAINTAIN THE HYDRAULIC PRESSURE OF THE REAR WHEELS, THE REAR WHEEL SOLENOID I\
NSIDE THE ABS ACTUATOR IS
PUT IN ªHOLDº MODE AND KEEPS THE HYDRAULIC PRESSURE TO THE BRAKE CYLINDER CONSTANT.
WHEN THE BRAKE CYLINDER HYDRAULIC PRESSURE IS REDUCED, THE PRESSURE REDU\
CTION MODE REDUCES AND CONTROLS
THE HYDRAULIC PRESSURE.
SYSTEM OUTLINE
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140
ABS AND TRACTION CONTROL
A24(A), A25(B), A26(C) ABS AND TRACTION ECU
(B) 21±GROUND : ALWAYS APPROX. 12 VOLTS
(B) 11±GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
(B) 10±GROUND : CONTINUITY WITH STOP LIGHT SW ON
(B) 2, (B) 13, (B) 22±GROUND : ALWAYS CONTINUITY
(B) 17±GROUND : CONTINUITY WITH PARKING BRAKE LEVER PULLED UP (PARKING BRAKE SW ON)
A 4(B), A 5(C), A 6(A) ABS ACTUATOR
(A) 1, (A) 2±GROUND : APPROX. APPROX. 12 VOLTS
(C) 1±GROUND : ALWAYS CONTINUITY
(B) 1, (B) 5, (B) 4, (B) 6±GROUND : APPROX. 1.15 (IGNITION SW OFF)
(B) 2±GROUND : APPROX. 5 (IGNITION SW OFF)
T3(A), T 4(B) TRACTION BRAKE ACTUATOR
(B) 2± (B) 4 : OPEN ABOVE APPROX. 134.5KG/CM2
(13189 KPA, 1910PSI)
CLOSED BELOW APPROX. 95KG/CM2 (9316 KPA, 1349PSI)
(A) 3± (A) 6 : APPROX. 2
(A) 2± (A) 5 : APPROX. 2
(A) 1± (A) 4 : APPROX. 2
S12 STOP LIGHT SW
2±1 : CLOSED WITH BRAKE PEDAL DEPRESSED
A 7, A 8, A30, A31 ABS SPEED SENSOR FRONT LH, RH, REAR LH, RH
1±2 : APPROX. 1.0(20 °C, 68°F)
T13(B), T14(A) TRACTION ECU
(A) 2±GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
(A) 15±GROUND : ALWAYS APPROX. 12 VOLTS
(A) 20, (A)14±GROUND : ALWAYS CONTINUITY
(A) 1±GROUND : CONTINUITY WITH PARKING BRAKE LEVER PULLED UP
(B) 2±GROUND : APPROX. 12 VOLTS WITH STOP LIGHT SW ON
(B) 13±GROUND : CONTINUITY WITH TRACTION CUT SW PUSHED ON
(B) 8±GROUND : ALWAYS APPROX. 12 VOLTS
P 3 PARKING BRAKE SW
1±GROUND : CLOSED WITH PARKING BRAKE LEVER PULLED UP
S 8 SUB THROTTLE ACTUATOR
2±1, 2±3 : APPROX. 0.9
5±4, 5±6 : APPROX. 0.9
: PARTS LOCATION
CODESEE PAGECODESEE PAGECODESEE PAGE
A 4B26C 326S 927
A 5C26C13B28S1229
A 6A26C14A28T 227
A 726D 128T 3A27
A 826D 228T 4B27
A1026E 226T 527
A24A28E 326T 629
A25B28E 9A28T1229
A26C28E10B28T13B29
A3030F 926T14A29
A3130P 329
B 126S 827
: RELAY BLOCKS
CODESEE PAGERELAY BLOCKS (RELAY BLOCK LOCATION)
219ENGINE COMPARTMENT LEFT624ENGINE COMPARTMENT LEFT
SERVICE HINTS
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142
ABS AND TRACTION CONTROL
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221
1E
19 1E 14
1H
11 1H 7
IK1
16 IK1 17
2
L
LH
TURN
A
5A 16 B 17 B16
C
23
1 IK2
5 IK2
4
SEAT BELT
ABS
TRAC
TRAC OFF
A
19 A 7B15 B 5B1
W±B
LG±R W
V
LG±R
TO ABS AND
TRACTION ECU
(
IND )
TO ABS AND
TRACTION ECU
( WT ) G
W G±Y
G±B
G±B G±Y WG
R±W
FROM
A/T INDICATOR SW
OIL PRESSURE SW RH
Y±B
O2
COMBINATION METER C12 , C 1 3
,C14
ABC
I23
WW
TO TDCL (
TRC )
IK 2
9
Y±B
I22
L±Y
IO1
7
L±Y
I23
L
L±Y
TO ENGINE AND
ECT ECU
(
W ) L±Y
TO CHAK
CONNECTOR (
W )
L
TO ABS AND
TRACTION ECU
(
WA ) L
TO CHECK
CONNECTOR (
LP )
IK2
2
L
W
1E
1
SEAT BELT WARNING
RELAY [INTEGRATION RELAY] CHECK ENGINE
B
3
L±Y
IK1
20
FROM TURN
SIGNAL FLASHER
3D
10
3A2
3A 1
W±B
G±O
OIL
G±O
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26
ELECTRICAL WIRING ROUTING
Position of Parts in Engine Compartment
A 1 A/C Ambient Temp. Sensor E 1 ECT Solenoid
A 2 A/C Lock Sensor and A/C Magnetic Clutch E 2 EFI Water Temp. Sensor
A 3 A/C High Pressure SW E 3 EGR Gas Temp. Sensor (for USA Spec.)
A 4 ABS Actuator E 5 Engine Hood Courtesy SW
A 5 ABS Actuator (w/ Traction Control) E 6 Engine Oil Level Warning SW
A 6 ABS Actuator (w/ Traction Control)
A 7 ABS Speed Sensor Front LH F 1 Front Airbag Sensor LH
A 8 ABS Speed Sensor Front RH F 2 Front Airbag Sensor RH
A 9 Air Flow Meter F 3 Front Clearance Light LH
A 10 Alternator F 4 Front Clearance Light RH
A 11 Alternator F 5Front Side Marker Light LH
A 33 ABS Actuator (w/o Traction Control) F 6 Front Side Marker Light RH F 7 Front Turn Signal Light LH
B 1 Brake Fluid Level SW F 8 Front Turn Signal Light RH
B 6 Back±Up Light SW (for M/T) F 9 Fuse Block
C 3 Check Connector H 1 Headlight Hi LH
C 6 Cornering Light LH H 2 Headlight Hi RH
C 7 Cornering Light RH H 3 Headlight Lo LH
C 8 Cruise Control Actuator H 4 Headlight Lo RH H 5 Horn LH
D 13 Distributor H 6 Horn RH
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28
ELECTRICAL WIRING ROUTING
Position of Parts in Instrument Panel
A 12 A/C Control Assembly C 9 CD Player
A 13 A/C Control Assembly C 10 Center Airbag Sensor Assembly
A 14 A/C Control Assembly C 11 Cigarette Lighter
A 15 A/C Control SW and Radio SW C 12 Combination Meter
A 16 A/C Evaporator Temp. Sensor C 13 Combination Meter
A 17 A/C Power Transistor C 14Combination Meter
A 18 A/C Power Transistor C 15 Combination SW
A 19 A/C Room Temp. Sensor C 16 Combination SW
A 20 A/C Solar Sensor C 17 Combination SW
A 21 A/T Indicator Light (for Shift Lever) C 19 Cruise Control ECU
A 22 ABS ECU (for M/T, w/o Traction Control) C 23 Clutch Start SW
A 23 ABS ECU (for M/T, w/o Traction Control) C 24 Cruise Control Clutch SW
A 24 ABS and Traction ECU
A 25 ABS and Traction ECU D 1 Diode (for Brake Fluid Level)
A 26 ABS and Traction ECU D 2 Diode (for Parking Brake)
A 27 Air Mix Control Servo Motor D 3 Diode (for Tension Reduser)
A 28 Air Vent Mode Control Servo Motor
A 29 Airbag Squib E 8 ECT Pattern Select SW
A 33 Air Inlet Control Servo Motor E 9 Engine and ECT ECU (for A/T) E 10 Engine and ECT ECU (for A/T)
B 2 Blower Motor E 11 Engine ECU (for M/T)
B 3 Blower Resistor (for Low Speed) E 12 Engine ECU (for M/T)
F 10 Fuel Lid Opener SW
G 1 Glove Box Light
G 2 Glove Box Light SW
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30
ELECTRICAL WIRING ROUTING
Position of Parts in Body
A 30 ABS Speed Sensor Rear LH D 10 Door Lock Motor, Door Unlock Detection SW and
A 31 ABS Speed Sensor Rear RH Door Open Detection SW LH
A 32 Auto Antenna Motor and Relay D 11 Door Lock Motor, Door Unlock Detection SW andDoor Open Detection SW RH
C 20 CD Automatic Changer D 12 Driving Position Memory and Return SW
C 21 CD Automatic Changer
C 22 Choke Coil F 11 Front Door Speaker LH F 12 Front Door Speaker RH
D 4 DAY/NIGHT Shift SW F 14 Fuel Lid Opener Solenoid
D 5 Door Courtesy Light LH F 15 Fuel Pump
D 6 Door Courtesy Light RH F 16 Fuel Pump ECU
D 7 Door Key Lock and Unlock SW LH F 17 Fuel Sender
D 8 Door Key Lock and Unlock SW RH F 18 Fuel Sender
D 9 Door Lock Control SW RH H 8 High Mount Stop Light (w/o Rear Spoiler)
H 9 High Mount Stop Light (w/ Rear Spoiler)
L 2 Licence Plate Light
L 3 Light Failure Sensor
L 4 Luggage Compartment Door Opener Motor
L 5 Luggage Compartment Key Unlock SW
L 6 Luggage Compartment Light SW
L 7 Luggage Compartment Light
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236
GROUND POINT
FRONT TURN SIGNAL
LIGHT LH
ENGINE HOOD
COURTESY SW
TRACTION PUMP AND
MOTOR
HEATER RELAY
ABS ACTUATOR RELAY
TELEPHONE
TRANSCEIVER
AND SPEAKER RELAY
ENGINE OIL LEVEL
WARNING SW
COMBINATION METER
(E1 )
EFI ECU
TRACTION ECU
CHECK CONNECTOR
(
E1 ) CORNERING LIGHT LH
FRONT SIDE MAKER
LIGHT LH
BRAKE FLUID LEVEL
SW
FRONT CLEARANCE
LIGHT LH
FRONT SIDE MAKER
LIGHT RH
FRONT CLEARANCE
LIGHT RH
ABS ACTUATOR
FRONT TURN SIGNAL
LIGHT RH
CRUISE CONTROL
ACTUATOR
OXYGEN SENSOR SUB
(
FOR USA SPEC. )
TDCL (
E1 )
WASHER LEVEL SW EFI MAIN RELAY
CORNERING LIGHT RH
A/C PRESSURE SW
(HI GH PRESSURE )
AIR FLOW METER POWER STERRI NG
PRESSURE SW
NOISE FI LTER
(
FOR IGNI TION SYSTEM ) E4
E10
E12 2
2
BS1 4 E4
E7
E1 E5
EB EA I23
I33
E1 6
I32
E20
E20
E20
IK2 24
ED EC IK1
1 BY1
5
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W± B W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B BR
BR
W±B BR
BR
BR
W±B BR
BR±B BR BR
BR
BR
W± B
W± B
W± B
W± B
W± B
W± B
W± B
W±B
W±B
BR
BR
BR
BR BR
BR
BR
W±B
BR BR
BR
( EO1 )
( E11 )
( E1 )
( EO2 )
I27BR
(
S1 )
( E1 )
NOISE FILTER (
FOR
IGNITION SYSTEM )W±B
W/ TRACTION SYSTEM
NOI SE FILTER
(
FOR DEFOGGER SYSTEM )
W±B
W±B
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238
GROUND POINT
RADIO AND PLAYER
WOOFER SPEAKER
AMP LIFIER
STEREO POWER
AMP LIFIER
CHOKE COIL
HIGH MOUNT STOP
LIGHT
HIGH MOUNT STOP
LIGHT
FUEL LID OPENER
SOLENOID
WIRELESS DOOR LOCK
ECU
POWER SEAT CONTROL
SW(
FOR PASSENGER' S
SEAT )
POWER SEAT ECU
( FOR PASSENGER' S
SEAT )
SEAT HEATER RH
( FOR PASSENGER' S
SEAT BACK )
PPS ECU
REMOTE CONTROL
MIRROR ECU I31
II
BV2
8
IQ2
12
B23 : PIONEER
B24 : NAKAMICHI
BR
BR
BR BR
(
W/O CD PLAYER )
( W/ CD PLAYER ) BR
BR
A/C POWER
TRANSISTOR
BLOWER RESISTOR
(
FOR LOW SPEED )
ABS ECU
ABS AND
TRACTION
ECU
TRACTION ECU (
GND )
DOOR LOCK CONTROL
SW
MIRROR HEATER RH DOOR LOCK MOTOR,
D OOR UNL OC K
DETECTION SW AND
DOOR OPEN DETECTION
SW RH DOOR KEY LOCK AND
UNLOCK SW RH
HEADLIGHT LO LH
I25
I14 B33
B6
B7
HEADLIGHT LO RH
B20
B21
B29
E1
I11 I12 I13
IJ
BL
Bd1
2
Bb14
IJ113
IP1 20
IN1
1
IE2
12
IE1
19
BX1
10
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B W±B W±B W±B W±B W±B
W±B
W±B W±B W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B
W±B W±B
W±B
W±B
W±B W±B
W±B
(
W/ REAR SPOILER )
( W/O REAR SPOILER )
W±BW±B
W±B W±B
(
GN D2 )
( GN D3 )
( GN D2 )
( GN D3 )
(
GN D1 )
W±B
W±B
BR
I27
W±B
W±B
WOOFER SPEAKER
AMP LIFIER
BU28
(W/O CD PLAYER )
P±L BR
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5678
3 LEXUS SC300(
Con' t )
1J
5
3B
53D 33A4
3D
53D 63B43D 13 1E
12 1H 12
IJ110
IK1 IK1 I K1 I K1 IK1 IK1
1 2 23 E
4D 1C 2C 3C 4C 5C 16C
E
1
C
18
3
3H
1
3A 1
1J
18
1E
10
3D
9
3D
IF
9
N1
A/T INDI CATOR SW
[ NEUTRAL ST ART SW AND
BACK±UP LIGHT SW]
A2 1
A/ T I NDI CAT OR LI GHT
( for shift lever )
GR±R
Y
G±O G
W
B± W
YYYWG L
GR
GR±R W± B
W± BW± B
W± B W± B
WL
W L
W
WL GR±R
GR±R
GR±R
Y
GR ±R
W± B
G
G±W R±B
GR
R±BGR
G
G±W
G
G±W L
R±B GR
G± O
Y
G
G± W R± B
GR
W L
G
G±W R±B
GR GR±R
Y
Y
B± W
12 11 13 14 16 1710
9
8
7
6
5
PRN D 2 L
4
L 2
D N R P
ECT POWER O/ D OFF
O5
O/DMAINSW ToABSECUandTractionECU
(
W/ Tr ac tion Cont rol )
<8±5>
ECT and A/T Indicator
BU1 8
BM
55 44
R± B R±B R±B
W± B
W± B
W±B R±B
Back±Up LightBACK±UP LIGHT
[ REAR COMB. LIGHT]
R1 1
RH
R10
LH
To TDCL º ECTº
<2±4>
10A
GA UGE
146 578
PRN D 2 L
C12 ,C 13 ,C 14
CD E
A/ T I NDI CATOR LI GHT
[COMB. METER] 7BU1
To Ti l t and Po we r
Telescopic ECU< 11±2>
GR
10 11 12 13 17 18 19 20 21
12345 6789
14 15 16 12 34 56 78
9 10 1112 13 14 1516 1718
17 18
1 2345 6789 10
23
22
21
20
19
15
14
13
12
11 16
C12C C13D C14E
A/T INDICATOR LIGHT
[COMB. METER]
GR Left kick panel Back panel c ent er
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