1995 TOYOTA SUPRA sensor

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)

Ts Terminal Circuit
CIRCUIT DESCRIPTION
The sensor check circuit detects abnormalities in the speed sensor signal which cannot be detected with the
diagnostic trouble code check.
Connecting terminals Ts and E1 of the DLC1 in the engine compartment starts the check.
Check for open and short in harness and connector between ABS (&TRAC)
ECU and DLC1, DLC1 and body ground (See page IN±30).
Turn ignition switch ON.
Measure voltage between terminals Ts and E1 of
DLC1.
Voltage: 10 ± 14 V
If ABS warning light does not blink even
after Ts and E1 are connected, the ECU may
be defective.
Repair or replace harness or connector.
Check and replace ABS (& TRAC) ECU.
INSPECTION PROCEDURE.
BR±114± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

P. BR±125
P. BR±126 ~ BR±128
P. BR±24
P. BR±126
P. BR±128P. BR±133
P. BR±165P. BR±134 ~ P. BR±163
Vehicle brought to workshop
Customer Problem Analysis
Check and Clear Diagnostic Trouble Codes (Precheck)
Problem Symptom ConfirmationSymptom Simulation
Diagnostic Trouble Code Check
Diagnostic Trouble Code ChartProblem Symptoms Chart
Check for Fluid LeakageCircuit InspectionSensor Check
Identification of Problem
Repair
Confirmation Test
Items insideare titles of pages in this manual,
with the page number in the bottom portion. See the
pages for detailed explanation.
Perform troubleshooting in accordance with the procedure on the following pages.
EndStep [2] , [5] , [9] , [11] : Diagnostic steps permitting the use
of the TOYOTA hand±held tester.
Symptom
does not occur
Symptom
occurs
Normal code
HOW TO PROCEED WITH TROUBLESHOOTING
BR±124± BRAKE SYSTEMTRACTION CONTROL SYSTEM (TRAC)

BR±134
BR±137
BR±137
BR±138
BR±138
BR±138
BR±138
BR±142
BR±145
BR±147
BR±149
BR±149
BR±152
BR±152
BR±155
BR±156
BR±157
Open or short in sub±throttle actuator circuit
Step motor does not move to a position decided by ECU
Sub±throttle valve does not move even when the sub±throttle
valve is controlled to fully open position by ECU
Right front wheel speed sensor signal malfunction
Left front wheel speed sensor signal malfunction
Right rear wheel speed sensor signal malfunction
Left rear wheel speed sensor signal malfunction
Low battery positive voltage or abnormally high battery
positive voltage
Malfunction in ABS or TRAC (BRAKE) control system
Open or short in NE signal circuit
Main throttle position sensor circuit malfunction
Open or short in main throttle position sensor circuit
Sub±throttle position sensor circuit malfunction
Open or short in sub±throttle position sensor circuit
Engine & ECT system malfunction
ECM communication circuit malfunction
ABS & TRAC ECU communication circuit malfunction
Malfunction in TRAC ECU
DiagnosisCodeTRAC Indicator Light
Blinking PatternSee page
DIAGNOSTIC TROUBLE CODE CHART
If a malfunction code is displayed during the diagnostic trouble code check, check the circuit listed for that code
in the table below and proceed to the relevant page.
HINT: If the TRAC indicator light lights up and the TRAC indicator light does not blink when the DTC is checked,
check the blinking pattern of the ABS warning light and troubleshoot the ABS system.
*
1: If a malfunction is detected in ABS the TRAC OFF indicator light lights up instead of the TRAC indicator
light.
*
2: The TRAC indicator light does not light up even if an error is detected
*3: If a malfunction is detected, the TRAC OFF indicator light lights up instead of the TRAC indicator light.
*4: Depending on the malfunction, the TRAC indicator light does not light up. BR±128
± BRAKE SYSTEMTRACTION CONTROL SYSTEM (TRAC)

PROBLEM SYMPTOMS CHART
If a normal code is displayed during the diagnostic trouble code check but the problem still occurs, check the
circuits for each problem symptom in the order given in the table below and proceed to the relevant troubleshoot-
ing page.
 
 Symptoms
 
 Inspection Circuit
 
 See page
 
 
 
 
 
 
 
 
TRAC does not
operate.
 
 
 
 
 
 
 
 
Only when 1. ~ 5, are all normal and the problem is still occurring,
replace the TRAC ECU.
1. Check the diagnostic trouble code, reconfirming that the Normal
code is output
2. IG power source circuit.
3. Check the hydraulic circuit for leakage.
4. Speed sensor circuit.
5. Park/neutral position switch circuit. 
 
 
 
 
 
 
 
BR±126
BR±142
BR±165
BR±138
AT1±81 or AT2±101
 
 TRAC indicator light
abnormal. 
 1. TRAC indicator light circuit.
2. TRAC ECU. 
 BR±162
 
 
 
 
 
TRAC OFF indicator
light abnormal.
 
 
 
 
 
Only when 1. and 2. are all normal and the problem is still occurring,
replace the TRAC ECU.
1. TRAC OFF indicator light circuit.
2. TRAC cut switch circuit.
 
 
 
 
 
BR±159
BR±159
 
 
 
 
Diagnostic trouble
code check cannot
be performed.
 
 
 
 
Only when 1. and 2, are all normal and the problem is still occurring,
replace the TRAC ECU.
1. TRAC indicator light circuit
2. Tc terminal circuit. 
 
 
 
BR±162
BR±163
± BRAKE SYSTEMTRACTION CONTROL SYSTEM (TRAC)BR±133

DTC 25 26 TRAC Sub±Throttle Valve
 DTC No. Diagnostic Trouble Code Detecting Condition Trouble area 
 
 
 
 
 
 
 
25
 
 
 
 
 
 
 
 
The difference between the sub±throttle
sensor signal voltage and the voltage
required by the step count is 1 V or more.
 
 
 
 
 
 
 
 

Sub±throttle actuator.

Throttle body (sub±throttle valve is stuck
or operation is faulty).

Sub±throttle position sensor.

Open or short in sub±throttle position sensor cir±
cuit.

ECM

TRAC ECU
 
 
 
 
 
 
 
26
 
 
 
 
 
 
 
Even when sub±throttle valve is driven to the
fully open position, input voltage at terminal
VTA2 of ECM does not come within range of
the specifications 3±4.5 V.
 
 
 
 
 
 
 

Sub±throttle actuator.

Throttle body (sub±throttle valve is stuck
or operation is faulty).

Sub±throttle position sensor.

Open or short in sub±throttle position sensor cir
cuit.

ECM

TRAC ECU
Remove air duct.
Open and close the sub±throttle valve manually and check
the condition during operation.
The valve should operate smoothly without catching.
HINT: If sub throttle actuator, sub±throttle valve, sub±throttle posi±
tion sensor and harness are free from any defect, ECM may
be defective.
If ECM is free from any defect, TRAC ECU may be defec±
tive.
± BRAKE SYSTEMTRACTION CONTROL SYSTEM (TRAC)BR±137

DTC 31 32 33 34 Speed Sensor Circuit
HINT: DTC No.31 is for the right front speed sensor.
DTC No.32 is for the left front speed sensor.
DTC No.33 is for the right rear speed sensor.
DTC No.34 is for the left rear speed sensor.
CIRCUIT DESCRIPTION
The speed sensor detects the wheel speed and sends the ap-
propriate signals to the ECU. These signals are used to control
both the ABS and TRAC control systems. The front and rear ro-
tors each have 48 serrations. When the rotors rotate, the magnet-
ic field emitted by the permanent magnet in the speed sensor
generates an AC voltage. Since the frequency of this AC voltage
changes in direct proportion to the speed of the rotor, the frequen-
cy is used by the ECU to detect the speed of each wheel.
Diagnostic Trouble Code Detecting ConditionTrouble areaDTC No.
Detection of any of conditions (1) through
(3):
At vehicle speed of 10 km/h (6 mph) or
more, pulses are not input for 5 sec.
Momentary interruption of the vehicle
speed sensor signal occurs at least 7
times in the time between switching the
ignition switch ON and switching it OFF.
Abnormal fluctuation of speed sensor
signals with the vehicle speed 20 km/h
(12 mph) or more.
Right front, left front, right rear and left
rear speed sensor.
Open or short in each speed sensor circuit.
ECU
BR±138± BRAKE SYSTEMTRACTION CONTROL SYSTEM (TRAC)