TOYOTA SUPRA 1995 Service Repair Manual

DTC 41 IG Power Source Circuit
CIRCUIT DESCRIPTION
This is the power source for the ECU, hence the CPU and the actuators.
 DTC No. Diagnostic Trouble Code Detecting Condition` Trouble area 
 
 
 
 
 
 
41
 
 
 
 
 
 
 
When either of the following (1) or (2) is
detected:
(1) Voltage at ECU terminal IG1 is less than
9.5 V for more than 10 sec. while vehicle
speed is 3 km/h (1.9 mph) or more.
(2) Voltage at ECU terminal IG1 is more than
17 V for more than 1.2 sec.
 
 
 
 
 
 
 

Battery

IC regulator

Open or short in power source circuit

ECU
Fail safe function: If trouble occurs in the power source circuit, the ECU cuts off current to the ABS solenoid relay
and prohibits ABS control.
BR±92± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

Check battery positive voltage.
Remove ABS (& TRAC) ECU with connectors still
connected.
1. Turn ignition switch ON.
2. Measure voltage between terminals IG1 and
GND of ABS (& TRAC) ECU connector.
Voltage: 10 Ð 14 V
Check and repair the charging system.
Voltage: 10 Ð 14 V
Check voltage between terminals IG1 and GND of ABS (& TRAC) ECU
connector.
Check and replace ABS (& TRAC) ECU.
INSPECTION PROCEDURE.
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±93

Check continuity between terminal GND of ABS (& TRAC) ECU
connector and body ground.
Measure resistance between terminals GND of
ABS (& TRAC) ECU connector and body ground.
Resistance: 1
or less
Check for short in all the harness and
components connected to ECU±IG fuse
(See attached wiring diagram).
Repair or replace harness or connector.
Check ECU±IG fuse.
Check for open in harness and connector be-
tween ABS (& TRAC) ECU and battery (See page
IN±30).
Remove ECU±IG fuse from J/B No. 1.
Check continuity of ECU±IG fuse.
Continuity BR±94
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

DTC 44 Lateral Acceleration Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects acceleration acting laterally on the vehicle. The sensor signal is used in ABS control. If the
sensor functions abnormally, the ABS warning light comes on but the ABS still operates.
 
 DTC No.
 
 Diagnostic Trouble Code Detecting Condition
 
 Trouble area
 
 
 
 
 
44
 
 
 
 
 
Either of the following (1) or (2) is detected:
(1) An open or short is detected in circuit
GS1 or GS2 for 1 sec.
(2) After the ignition is turned ON, the test
signal is output by GST. During this time,
a trouble signal is detected for 0.5 sec. 
 
 
 
 

Lateral acceleration sensor

Open or short in lateral acceleration sensor circuit

ECU
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±95

Check for open and short in harness and connector between sensor and
ECU (See page IN±30).
1. Remove ABS (& TRAC) ECU with connec±
tors still connected.
1. Disconnect sensor connector.
3. Turn ignition switch ON.
Measure voltage between terminals GS1, GS2,
GST of ECU and body ground.
Voltage:
GS1, GS2: 10 Ð 14 V
GST: As shown below
Check voltage between terminals GS1, GS2, GST of ECU and body ground.
Repair or replace harness or connector.
Check and replace ABS (& TRAC) ECU.
Check and replace lateral acceleration sensor.
INSPECTION PROCEDURE.
BR±96± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

DTC 51 ABS Pump Motor Lock
CIRCUIT DESCRIPTION
 
 DTC No.
 
 Diagnostic Trouble Code Detecting Condition
 
 Trouble area
 
 51 
 
Pump motor is not operating normally during
initial check. 
 
ABS pump motor
Fail safe function: If trouble occurs in the ABS pump motor, the ECU cuts off the current to the solenoid relay
and prohibits ABS control.
WIRING DIAGRAM
See page BR±72
INSPECTION PROCEDURE
See inspection of ABS actuator (See page BR±44).
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±97

DTC 55 Brake Fluid Level Warning Switch Circuit
CIRCUIT DESCRIPTION
The brake fluid level warning switch sends the appropriate signal to the ECU when the brake fluid level drops.
 DTC No. Diagnostic Trouble Code Detecting Condition Trouble area
 
 
 
 
55
 
 
 
 
Voltage at ECU terminal LBL is 0 V
continuously for 10 sec. or more.
 
 
 
 

Brake fluid level

Brake fluid level warning switch

Short in brake fluid level warning switch circuit

ECU
Fail safe function: If trouble occurs in this circuit, the ECU cuts off current to the TRAC solenoid relay and prohib-
its TRAC control. BR±98
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

Check brake fluid level.
Check brake fluid level warning switch.
Check and repair brake fluid leakage and
add fluid.
Replace brake fluid level warning switch.
Repair or replace harness or connector.
Check and replace ABS & TRAC ECU.
Check for short in all the harness and components connected to brake fluid
level warning light (See page IN±30).
See page BE±52.
Check the amount of fluid in the brake reservoir.
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±99

DTC 58 TRAC Pump Motor Circuit
CIRCUIT DESCRIPTION
This motor is used to apply hydraulic pressure for the rear wheel brakes during TRAC control.
 DTC No. Diagnostic Trouble Code Detecting Condition Trouble area
 






58





 
Conditions (1) through (3) continue for 2 sec.
or more:
(1) TRAC motor relay: Normal
(2) TRAC motor: OFF
(3) Voltage of ABS & TRAC ECU terminal
MTT: 4±8 V 
 
 
 
 
 

TRAC pump motor

Open in TRAC pump motor circuit

ECU
Fail safe function: If trouble occurs in this circuit, the ECU cuts off current to the TRAC solenoid relay and
prohibits TRAC control.
BR±100± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

Check TRAC pump motor.
Check for open and short in harness and connector between TRAC pump
motor and ECU (See page IN±30).
Replace TRAC pump motor.
Measure resistance between terminal 1 of TRAC
pump motor connector and body ground.
Resistance: 1
or less
Check and replace ABS & TRAC ECU.
Check continuity between terminal 1 of TRAC pump motor connector and
body ground.
Repair or replace harness or connector.
Repair or replace harness or connector.
Terminals 1 and 3
Terminals 2 and 3
Continuity (Reference
value 100

or less)
Continuity (Reference
value 4 ~ 6

or less)
Disconnect TRAC pump motor connector.
Check continuity between each terminal of TRAC
pump motor shown below.
INSPECTION PROCEDURE.
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±101