sensor LEXUS SC400 1991 Service Repair Manual

OKNG
NGOK
6Check for open and short in harness and connector between terminal VTA2 of ECM and sub±
throttle position sensor (See page IN±33
)
Repair or replace harness or connector.
Adjust or replace sub±throttle position sensor
(See page EG±333 or EG±205 ).
7Check voltage between terminal IDL2 of TRAC ECU and body ground.
C
OK
PTurn ignition switch on.
Measure voltage between terminal IDL2 or TRAC ECU
connector and body ground, when the sub±throttle
valve is fully closed and fully opened.
Check and replace TRAC ECU.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±213
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OKNG
10Check sub±throttle position sensor (See page EG±609 or EG±389 ).
Adjust or replace sub±throttle position sensor (See page
EG±333 or EG±205 ).
Check and replace ECM.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±215
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TORQUE SPECIFICATIONS
BR03B±0G\
 
\

\
Part tightened
 

N
Vm
 

kgf
Vcm
 

ft
Vlbf
\
 \
Master cylinder x Piston stopper bolts 10 100 7
\
 \
Master cylinder x Reservoir 1.7 17.5 15.2 in. Vlbf
\
 
\

\
Master cylinder x Brake booster 

13 

130 

9
\
 \
Brake tube union nut 15 155 11
\
 \
Brake booster clevis lock nut 25 260 19
\
 \
Brake booster x Pedal bracket 15 150 11\
 
\

\
Bleeder plug (TRAC actuator and TRAC accumulator)
 

8.3
 

85
 

74 in.
Vlbf
\
 \
Bleeder plug 11 11 0 8
\
 \
Front disc brake torque plate x Steering knuckle 11 8 1,200 87
\
 \
Front disc brake cylinder installation bolt 34 350 25\
 
\

\
Front disc brake cylinder x Flexible hose bolt
 

30
 

310
 

22
\
 \
Rear disc brake torque plate x Axle carrier 104 1,065 77
\
 \
Rear disc brake cylinder installation bolt 34 350 25
\
 
\

\
Rear disc brake x Flexible hose union bolt 

30 

310 

22
\
 \
Parking brake lever x Floor 59 600 43
\
 \
Parking brake cable No.1 x Floor 9 80 69 in.
Vlbf
\
 \
Parking brake cable retainer x Floor 5.4 55 48 in. Vlbf\
 
\

\
Parking brake cable clamp x Floor
 

19
 

190
 

14
\
 \
ABS actuator x Actuator bracket 5.4 55 48 in.
Vlbf
\
 \
ABS actuator bracket x Body 19 195 14
\
 
\

\
Front speed sensor installation bolt 

7.8 

80 

69 in.
Vlbf
\
 \
Rear speed sensor installation bolt 7.8 80 69 in. Vlbf
\
 \
TRAC pump bracket x Body 19 195 14
\
 \
TRAC pump or accumulator x Union bolt 46 465 34
BR±230±
BRAKE SYSTEM SERVICE SPECIFICATIONS
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BR0F2±02
SPEED SENSOR
SPEED SENSOR REMOVAL AND
INSTALLATION
Remove and install the parts, as shown.
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±71
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TROUBLESHOOTING
How to proceed with troubleshooting
Perform troubleshooting in accordance with the procedure on the followin\
g pages.

CUSTOMER PROBLEM ANALYSIS
Using the customer problem analysis check sheet for reference, ask the c\
ustomer in as much detail as
possible about the problem.
CHECK AND CLEAR THE DIAGNOSTIC TROUBLE CODES (PRECHECK)
If the ABS warning light lights up, and the ABS does not operate, the ECU \
stores diagnostic trouble codes
corresponding to the problem in memory.
Before confirming the trouble, 1st check the diagnostic trouble codes for any \
malfunction codes stored in
memory. When there are malfunction codes, make a note of them, then clear them \
and proceed to ª  Prob-
lem Symptom Confirmationº.
 PROBLEM SYMPTOM CONFIRMATION,  SYMPTOM SIMULATION
Confirm the problem symptoms. If the problem does not reoccur, simulate the problem by initially checking
the circuits indicted by the diagnostic trouble code in step , using ªProblem simulation methodº.
 DIAGNOSTIC TROUBLE CODE CHECK
Check the diagnostic trouble codes. If a malfunction code is output, proceed \
to ª  Diagnostic Trouble
Code Chartº. If the normal code is output, proceed to ª  Problem Symptoms Chartº. Be sure to proceed
to ª  diagnostic Trouble Code Chartº after steps and  are completed.
If troubleshooting is attempted only by following the malfunction code sto\
red in the memory, errors could
be made in the diagnosis.
 DIAGNOSTIC TROUBLE CODE CHART
If a malfunction code is confirmed in the diagnostic trouble code check,\
proceed to the inspection proce-
dure indicated by the matrix chart for each diagnostic trouble code.
 PROBLEM SYMPTOMS CHART
If the normal code is confirmed in the diagnostic trouble code check, perf\
orm inspection in accordance with
the inspection order in the problem symptoms chart.
 CIRCUIT INSPECTION
Proceed with diagnosis of each circuit in accordance with the inspection\
order confirmed in  and .
Determine whether the cause of the problem is in the sensor, actuators, wire harness and connectors or
the ECU.
\b SENSOR CHECK
Use the ABS warning light to check if each of the signals from speed sensors are being input correctly to
the ECU. Instructions for this check are given in the circuit inspection.
[10] REPAIRS
After the cause of the problem is located, perform repairs by following the i\
nspection and replacement pro-
cedures in this manual.
[11] CONFIRMATION TEST After completing repairs, confirm not only that the malfunction is eliminated\
, but also conduct a test drive
to make sure the entire ABS system is operating correctly. (In vehicles with the TRAC system, also check
the TRAC system.)
BR±72
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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SPEED SENSOR SIGNAL CHECK
1. Turn the ignition switch to OFF.
2. Using SST, connect terminals Ts and E1 of DLC1.SST 09843±18020
3. Start the engine.
4. Check that the ABS warning light blinks. HINT: If the ABS warning light does not blink, inspect the ABS
warning light circuit (see page BR±144).
5. Drive vehicle straight forward. HINT: Drive vehicle faster than 45 km/h (28 mph) for several
seconds.
6. Stop the vehicle.
7. Using SST, connect terminals Tc and E1 of DLC1.
SST 09843±18020
8. Read the number of blinks of the ABS warning light. HINT: See the list of diagnosis trouble codes shown on the
next page.
If every sensor is normal, a normal code is output (A cycle of
0.25 sec. on and 0.25 sec. OFF is repeated).
If 2 or more malfunction are indicated at the same time, the
lowest numbered code will be displayed 1st.
9. After performing the check, disconnect terminals Ts and E1,Tc and E1 of DLC1, and ignition switch turned off.
BR±80
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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ECU DATA MONITOR USING LEXUS HAND±HELD TESTER
1. Hook up the LEXUS hand±held tester to the DLC2.
2. Monitor the ECU data by following the prompts on the testerscreen.
HINT: LEXUS hand±held tester has a ªSnapshotº function
which records the monitored data.
Please refer to the LEXUS hand±held tester operator's
manual for further details.
Diagnostic Trouble Code of Speed Sensor Check Function
 Code No.\
\
Diagnosis Trouble Area 

71
\


\
Low output voltage of right front speed sensor
 



Right front speed sensor
 
71
\
\
Low output voltage of right front speed sensor
 
Sensor installation
 72\
\
Low output voltage of left front speed sensor 
Left front speed sensor
 72\
\
Low output voltage of left front speed sensor 
Sensor installation
 
73
\
\
Low output voltage of right rear speed sensor
 
Right rear speed sensor
 73\
\
Low output voltage of right rear speed sensor 
Sensor installation
 
74
\
\
Low output voltage of left rear speed sensor
 
Left rear speed sensor 74\
\
Low output voltage of left rear speed sensor 
Sensor installation 

75
\


\
Abnormal change in output voltage of right front speed
sensor 



Right front speed sensor rotor
 

76
\


\
Abnormal change in output voltage of left front speed
sensor 



Left front speed sensor rotor
 

77
\


\
Abnormal change in output voltage of right rear speed
sensor 



Right rear speed sensor rotor
 

78\


\
Abnormal change in output voltage of left rear speed
sensor 



Left rear speed sensor rotor
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±81
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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 page for
troubleshooting.
 Symptoms\
 \
Inspection Circuit See page
 


ABS does not oper-
ate.\
 
\

\

Only when 1.±4. are all normal and the problem is still occurring,
replace the ABS (& TRAC) ECU. 


BR±76
 


\
 
\

\

1. Check the diagnostic trouble code, reconfirming that the nor-
mal code is output. 

BR±122
BR±118
 \
 \
2. IG Power Source Circuit. BR±65 or 68 


\
 
\

\
3. Speed sensor circuit.
 


 




\
 
\


\

\

4. Check the ABS actuator with a checker.
If abnormal, check the hydraulic circuit for leakage (see page
BR±138). 




 


ABS does not oper-
ate efficiently.\
 
\

\

Only when 1.±4. are all normal and the problem is still occurring,
replace the ABS (& TRAC) ECU. 


BR±76
 


\
 
\

\

1. Check the diagnostic trouble code, reconfirming that the nor-
mal code is output. 


BR±118
BR±142
 \
 \
2. Speed sensor circuit. BR±65
or 68
 \
 \
3. Stop light switch circuit 
 




\
 
\


\

\

4. Check the ABS actuator with a checker.
If abnormal, check the hydraulic circuit for leakage (see page
BR±138). 




 


ABS warning light ab-
normal.\
 
\

\

1. ABS warning light circuit. 

BR±144
 \
 \
2. ABS (& TRAC) ECU. 
 




Diagnostic trouble
code check cannot
be performed.\
 
\


\

\

Only when 1. and 2. are all normal and the problem is still occur-
ring, replace the ABS (& TRAC) ECU. 




BR±144
 \
 \
1. ABS warning light circuit BR±148 


\
 
\

\
2. To terminal circuit.
 


 


Speed sensor signal
check cannot be per-
formed.\
 
\

\

1. Ts terminal circuit. 


BR±150
 


\
 
\

\
2. ABS (& TRAC) ECU.
 


BR±82±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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DTC
31, 32,
33, 34,35, 36
Speed Sensor Circuit
CIRCUIT DESCRIPTION
The speed sensor detects the wheel speed and sends the ap-
propriate signals to the ECU. These signals are used for control
of both the ABS and TRAC control systems. The front and rear
rotors each have 48 serrations. When the rotors rotate, the
magnetic field emitted by the permanent magnet in the speed
sensor generates an AC voltage. Since the frequency of this
AC voltage changes in proportion to the speed of the rotors
(wheels) the frequency is used by the ECU to detect the speed
of each wheel.
BR3583
BR3582
DTC No.DTC Detecting ConditionTrouble Area
31, 32,
33, 34
Detection of any of conditions (1) through (3):
(1) At vehicle speed of 10 km/h (6 mph) or more,
pulses are not input for 5 sec.
(2) Momentary interruption of the vehicle speed sen-
sor signal occurs at least 7 times in the time between
switching the ignition switch ON and switching it OFF.
(3) 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
35
Vehicle speed sensor signal is not input for about 1 sec.
while the left front and right rear with the vehicle speed
sensor signals are being checked IG switch ON.
Open in left front, right rear speed sensor cir-
cuit.

ECU
36
Vehicle speed sensor signal is not input for about 1 sec.
while the right front and left rear vehicle speed sensor
signals are being checked with the IG switch ON.
Open in right front, left rear speed sensor cir-
cuit.

ECU
HINT: DTC No. 31 is for the right front wheel speed sensor.
DTC No. 32 is for the left front wheel speed sensor.
DTC No. 33 is for the right rear wheel speed sensor.
DTC No. 34 is for the left rear wheel speed sensor.
Fail safe function: If trouble occurs in the speed sensor circuit, the ECU cuts off current to the ABS
solenoid relay and prohibits ABS control.
BR±118
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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OKNG
OKNG
INSPECTION PROCEDURE
1Check speed sensor.
C
OK
P
OK
C
P
OK
C
OK
1. Remove front fender liner.
2. Disconnect speed sensor connector.
Measure resistance between terminals 1 and 2 of speed
sensor connector.
Resistance: 0.6 ± 1.8 k 
Measure resistance between terminals 1 and 2 of speed
sensor connector and body ground.
Resistance: 1 M or higher
1. Remove rear fender liner.
2. Disconnect speed sensor connector.
Measure resistance between terminals 1 and 2 of speed
sensor connector.
Resistance: 0.6 ± 1.7 k 
Measure resistance between terminals 1 and 2 of speed
sensor connector.
Resistance: 1 M or higher
Replace speed sensor.
2Check for open and short in harness and connector between each speed sensor a\
nd ECU (See
page IN±33).
Repair or replace harness or connector.
BR±120
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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