LEXUS SC400 1991 Service Repair Manual

Location of Connectors in Body
BR±92±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±93
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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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WIRING DIAGRAM
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±95
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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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±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±99
WIRING DIAGRAM
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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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