relay LEXUS SC400 1991 Service Manual PDF

DESCRIPTION
The combination meter has various meters and gauges which show the vehicle'\
s condition, warning lights which
monitor abnormalities in the vehicle and inform the driver, indicator lights which inform the driver of the condition
of each part of vehicle, and a function for illumination and brightness ad\
justment of meters and gauges.
The component parts of this system and their functions are described in \
the following table.
Parts NameFunction
SpeedometerThe speedometer needle moves in accordance with signals from the speed s\
ensor to
indicate the vehicle's speed.
TachometerThe tachometer needle moves in accordance with signals from the igniter \
to indicate the
engine's speed.
Water Temperatrue
GaugeThe water temperature gauge's needle moves in accordance with signals from the send-
er gauge and indicates the temperature of the engine coolant.
Fuel GaugeThe fuel gauge needle moves in accordance with signals from the sender g\
auge, indicat-
ing the amount of fuel remaining in the fuel tank.
OdometerThe odometer counts the total distance traveled by the vehicle in accord\
ance with pulse
signals from the speed sensor.
Twin Trip Switch
The twin trip meter counts the distance traveled by the vehicle in accor\
dance with pulse
signals from the speed sensor. It can be reset using a switch and can be used to switch
between trip meters A and B.
Circuit Plate
This plate contains the circuitry for each meter and gauge and for each \
warning light and
indicator light, as well as an internal engine oil level warning drive c\
ircuit, drive circuits for
the odometer and trip meter and brightness adjustment circuitry for each\
indicator.
Speed SensorMounted in the transmission, this sensor outputs pulse signals to the co\
mbination meter
in accordance with the speed of the output shaft.
Twin Trip SwitchOperation of this switch switches between the A and B trip meters and se\
nds reset sig-
nals to the combination meter.
Water
Temperature Sender
GaugeThis sender converts engine coolant temperatures to a resistance value i\
n signal form to
the combination meter.
Fuel Sender GaugeThis sender converts the level of fuel remaining in fuel tank to resista\
nce value and
sends the resistance value in signal form to combination meter.
Rheostat Light
Control VolumeIn order to adjust the degree of illumination of the combination meter, the resistance val-
ue of the built±in variable resistor is sent to the combination meter\
and rheostat light
control.
Fuel Level Warning
SwitchWhen the level of fuel remaining falls below a predetermined level, cont\
inuity is estab-
lished with this switch, which is built into the fuel sender gauge, caus\
ing a warning light
to light up.
Low Oil Pressure
Warning SwitchThis switch is mounted on the engine block. Continuity is established in\
this switch when
the oil pressure is low, causing a warning light to light up.
Integration Relay (Seat
Belt Warning Relay)
This relay receives current from fuse GAUGE and DOME and is connected to\
each
buckle switch, door courtesy switch, key unlock warning switch and warni\
ng light. As
part of the seat belt warning system, it sounds a chime and lights a war\
ning light when
seat belts are unfastened. As part of the key unlock warning system, it \
sounds a chime
when the set conditions are fulfilled.
Light Failure SensorThis sensor senses when a bulb in rear combination light is burnt out an\
d lights up a
warning light.
BE±96±
BODY ELECTRICAL SYSTEM Combination Meter
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NOYES
OKNG
OKNG
OKNG
OKNG
INSPECTION PROCEDURES
1Is diagnostic trouble code output?
Perform diagnostic trouble code check on page BR±184.
Repair circuit indicated by the code output.
2Check TRAC cut switch
C
OK
P1. Remove TRAC cut switch.
2. Disconnect TRAC cut switch connector.
Measure re sistance between terminals 1 and 2 of TRAC
cut switch when TRAC cut switch is on and off.
Replace TRAC cut switch.
3Check for open and short in harness and connector between terminal CSW of TRA\
C ECU and
TRAC cut switch and body ground (See page IN±33
).
Repair or replace harness or connector.
4Check TRAC OF indicator light.
See combination meter troubleshooting on page BE±191.
Repair or replace combination meter.
5Check for open and short in harness and connector between terminal WT of TRAC ECU \
and bat-
tery or TRAC solenoid relay (See page IN±33
).
Repair or replace harness or connector.
Check and replace TRAC ECU.
BR±224±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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ABS ACTUATOR INSPECTION
BR0F1±03
HINT: Using the ABS actuator checker (SST), check the op-
eration of the actuator. If the actuator does not operate,
check the operation of sub±wire harness G according to
instructions on pages BR±97 and BR101. If the solenoid and/
or pump motor relay are abnormal, replace the relay and in-
spect the actuator operation again.
w/o TRAC:
1. INSPECT BATTERY POSITIVE VOLTAGE
Battery positive voltage:
10±14V
2. DISCONNECT CONNECTORS FROM ACTUATORDisconnect the 2 connectors from the actuator.
3. CONNECT ACTUATOR CHECKER (SST) TO ACTUATOR
(a) Connect the actuator checker (SST) to the actuator side wire harnesses via the sub±wire harnesses (SST), as shown.
SST 09990±00150, 09990±00210, 09990±00250 and09990±00280
(b) Connect the red cable of the checker to the battery positive (+) terminal and the black cable to negative (±) terminal.
Connect the black cable of the sub±wire harnesses to the
battery negative (±) terminal or body ground.
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±65
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DTC11, 12ABS Solenoid Relay Circuit
CIRCUIT DESCRIPTION
This relay supplies power to each ABS solenoid. After the ignition switch is\
turned on, if the initial check is OK,
the relay goes on.
DTC No.DTC Detecting ConditionTrouble Area
11
Conditions (1) and (2) continue for 0.2 sec. or more:
(1) ABS solenoid relay (SR) terminal voltage: Battery
positive voltage
(2) Solenoid relay monitor (AST) terminal voltage: 0V
ABS solenoid relay

Open or short in ABS solenoid relay circuit

ECU
12
Conditions (1) and (2) continue for 0.2 sec. or more:
(1) ABS solenoid relay (SR) terminal voltage: 0V
(2) Solenoid relay monitor (AST) terminal voltage: Bat- tery positive voltage
ABS solenoid relay

B+ short in ABS solenoid relay circuit

ECU
Fail safe function: If trouble occurs in the solenoid relay circuit, th\
e ECU cuts off current to the solenoid
relay and prohibits ABS control.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±94±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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OKNG
OKNG
INSPECTION PROCEDURE
1Check voltage between terminals 1 and 2 of R/B No. 6 (For ABS solenoid relay\
).
C
OK
PRemove ABS solenoid relay from R/B No. 6.
Measure voltage between terminals 1 and 2 of R/B No.
6 (for ABS solenoid relay).
Voltage: 10 ± 14 V
Check and repair harness or connector.
2Check continuity between terminal 3 or R/B No. 6 (for ABS solenoid relay) a\
nd terminal AST of
ABS (& TRAC) ECU.
C
OK
Hint
Check continuity between 3 of R/B No. 6 (for ABS sole-
noid relay) and terminal AST of ABS (& TRAC) ECU.
Continuity
There is a resistance of 4 ~ 6
between terminals BS
and AST of ABS actuator.
Repair or replace harness or ABS actuator.
BR±96
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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OKNG
OKNG
3Check ABS solenoid relay.
C
OK
P
C
OK
Remove solenoid relay from R/B No. 6.
Check continuity between each terminal of ABS sole-
noid relay shown below.
1. Apply battery voltage between terminals 4 and 6.
2. Check continuity between each terminal of ABS so-
lenoid relay shown below.
Replace ABS solenoid relay.
4Check for open and short in harness and connector between ABS solenoid r\
elay and ABS (&
TRAC) ECU (See page IN±33).
Repair or replace harness or connector.
If the same code is still output after the diagnostic trouble code is dele\
ted, check the contact condition
of each connection.
If the connections are normal, the ECU may be defective.
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±97
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DTC13, 14ABS Motor Relay Circuit
CIRCUIT DESCRIPTION
The ABS motor relay supplies power to the ABS pump motor. While the ABS is activate the ECU switches the
motor relay ON and operates the ABS pump motor.
DTC No.DTC Detecting ConditionTrouble Area
13
Conditions (1) and (2) continued for 0.2 sec. or more:
(1) ABS motor relay (MR) terminal voltage: Battery positive voltage
(2) Motor relay monitor (MT) terminal voltage: 0V

ABS motor relay

Open or short in ABS motor relay circuit

ECU
14
Conditions (1) and (2) continued for 4 sec. or more:
(1) ABS motor relay (MR) terminal voltage: 0V
(2) Motor relay monitor (MT) terminal voltage: Battery positive voltage

ABS motor relay

B+ short in ABS motor relay circuit.

ECU
Fail safe function: If trouble occurs in the motor relay circuit, the ECU cuts off the current to the solenoid
relay and prohibits ABS control.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±98±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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OKNG
OKNG
INSPECTION PROCEDURE
1Check voltage between terminal 1 of ABS motor relay and body ground.
C
OK
PRemove ABS motor relay from R/B No. 6.
Measure voltage between terminal 1 of ABS motor relay
and body ground.
Voltage: 10 ± 14 V
Check and repair harness or connector
2Check continuity between terminal 2 of R/B No. 6 (for ABS motor relay) and terminal MT of ABS
(& TRAC) ECU.
C
OK
Hint
Check continuity between terminal 2 or R/B No. 6 (for
ABS motor relay) and terminal MT of ABS (& TRAC)
ECU.
Continuity
There is a resistance of 4 ± 6 between terminals BM and
MT for ABS actuator.
Repair or replace harness or ABS actuator.
BR±100
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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OKNG
OKNG
3Check ABS solenoid relay.
C
OK
P
OK
C
Remove solenoid relay from R/B No. 6
Check continuity between each pair of terminal of motor
relay shown below.
1. Apply battery voltage between terminals 3 and 4.
2. Check continuity between terminals shown below.
Replace ABS motor relay.
4Check for open and short in harness and connector between ABS motor relay and ABS (&
TRAC) ECU (See page IN±33).
Repair or replace harness or connector.
If the same code is still output after the diagnostic trouble code is dele\
ted, check the contact condition
of each connection.
If the connections are normal, the ECU may be defective.
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±101
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DTC15, 16TRAC Solenoid Relay Circuit
CIRCUIT DESCRIPTION
This relay circuit supplies power to each traction actuator solenoid.When th\
e ignition switch is turned on, the
relay goes on.
DTC No.DTC Detecting ConditionTrouble Area
15
Conditions (1) through (3) continue for 0.2 sec.or more:
(1) TRAC solenoid relay (TSR) terminal voltage: Bat-
tery positive voltage
(2) All TRAC actuator solenoid: OFF(3) All TRAC ac-
tuator solenoid monitor voltage (in ECU): 0V

TRAC solenoid relay

Open or short in TRAC solenoid relay circuit

ECU
16
Conditions (1) through (3) continue for 0.2 sec.or more:
(1) TRAC solenoid relay (TSR) terminal voltage: 0V
(2) All TRAC actuator solenoid: OFF
(3) TRAC actuator solenoid monitor voltage (in ECU):
Battery positive voltage

TRAC solenoid relay

B+ short in TRAC solenoid relay circuit

ECU
Fail safe function: If tr ouble occurs in this relay circuit, the ECU cuts off the current to the ABS and TRAC
solenoid relays and prohibits ABS and TRAC control.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±102±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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