sensor LEXUS SC300 1991 Service Repair Manual

ConnectionCheck forTester connectionConditionSpecified value
A19 A15Trip switch A/BPushContinuity
Trip switchContinuity
A19±A15Trip switch A/BFreeNo continuityTrip switchContinuity
A20 A15Trip switch RESETPushContinuityA20±A15Trip switch RESETFreeNo continuity
DOME
FuseVoltageA11±GroundConstantBattery positive voltage
Speed
SVoltageA13 A15
Ignition
switch
*3 Revolve propeller shaft0V
11 V
SensorVoltageA13±A15switch
ON*3 Stop propeller shaft0V or 11V
C1±GroundPBattery positive voltage
C2±GroundIgnitionRBattery positive voltage
Neutral start
it hVoltageC3±Ground
Ignition
switch
ON andNBattery positive voltageswitchVoltageC4±GroundON and
shift leverDBattery positive voltage
C5±Ground
shift lever
position2Battery positive voltage
C16±Ground
osition
LBattery positive voltage
O/D OFFContinuityC18 GroundO/D OFF switchONContinuity
SwitchContinuityC18±GroundO/D OFF switchOFFNo continuity
AlternatorContinuityC15±GroundEngine stopContinuity
ºLº terminalVoltageC14±GroundEngine runningBattery positive voltage
FuelContinuityA7 GroundFuel remainderFullNo continuity
SenderContinuityA7±GroundFuel remainderEmptyContinuity
GaugeFull, Approx. 79.3 mm
(3.12 in.)Approx. 6

ResistanceA8±C8Float
position1/2, Approx. 193.1 mm
(76.0 in.)Approx. 32.5

Empty, Approx. 308.1 mm
(12.13 in.)Approx. 97

*Window
washer level
ContinuityB9±GroundON (float down)Continuitywasher level
warning
switchContinuityB9 Ground
(Canada)OFF (float up)No continuity
Brake fluidBrake fluid levelON (float down)Continuity
Level warning
Brake fluid level
warning SWOFF (float up)No continuity
SW and
Parking brake
SW
ContinuityC13±GroundParking brake
ON (Depress the Ped-
al))Continuity
SWParking brake
SWOFF (Release the Ped-
al)No continuity
Low oil
PressureContinuityC19 GroundEngine condition
RunningNo continuity
Pressure
Warning SWContinuityC19±GroundEngine conditionStopContinuity
Door courtesyContinuityC12 GroundDriver's andOpen (ON)Continuityy
SwitchContinuityC12±GroundDriver s and
passenger's doorClosed (OFF)No continuity
IGN fuseVoltageC14 GroundIgnition switchONBattery positive voltageVoltageC14±GroundIgnition switchLOCK or ACCNo voltage
CIG fuseVoltageA6 GroundIgnition switchACC or ONBattery positive voltageVoltageA6±GroundIgnition switchLOCK or STARTNo voltage
BE±107±
BODY ELECTRICAL SYSTEM Combination Meter
WhereEverybodyKnowsYourName

(Speed Sensor)
REMOVAL AND INSTALLATION OF
SPEED SENSOR
1. REMOVE SPEED SENSOR(a) Jack up the vehicle.
(b) Disconnect connector and control rod.
(c) Remove a bolt and sensor.
2. INSTALL SPEED SENSOR For installation, follow the removal procedure in reverse.
INSPECTION OF SPEED SENSOR
INSPECT SPEED SENSOR(Operation)
(a) Connect the positive (+) lead from battery to terminal 1and negative (±) lead to terminal 2.
(b) Connect the positive (+) lead from tester to terminal 3 and negative (±) lead to terminal 2.
(c) Revolve shaft.
(d) Check that there is voltage change from approx. 0V to 11V or more between terminal 2 and 3.
HINT: The voltage change should be 4 times per each revolu-
tion of the speed sensor shaft.
If operation is not as specified, replace the sensor.
(Sensor circuit)
Disconnect connector from sensor and inspect the connector
on wire harness side as shown.
Check forTester connectionConditionSpecified value
Voltage1 GroundIgnition switchONBattery positive voltageg1±GroundIgnition switch
positionLOCK or ACCNo voltage
If circuit is not as specified, inspect power source or wire
harness.
±
BODY ELECTRICAL SYSTEM Combination MeterBE±110
WhereEverybodyKnowsYourName

TROUBLESHOOTING
How to proceed with troubleshooting
Perform troubleshooting in accordance with the procedure on the followin\
g page.

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 TRAC indicator light lights up, and the TRAC control does not ope\
rate, the ECU stores diagnostic
trouble codes corresponding to the problem in memory.
Before confirming the trouble, first check the diagnostic trouble code for any\
malfunction codes stored in
memory. When there are malfunction codes, make a note of them, then clear them and proceed to ª 
Problem 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 indicated 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 is \
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 TRAC system is operating correctly. And also check the ABS is operating correctly.
BR±166
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
WhereEverybodyKnowsYourName

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
 


TRAC does not oper-
ate.\
 
\

\

Only when 1.~5. are all normal and the problem is still occurring, repla\
ce
the TRAC ECU. 

BR±170
 


\
 
\

\

1. Check the diagnostic trouble code, reconfirming that the normal code \
is
output. 


BR±192
 \
 \
2. IG Power Source Circuit. BR±228
 


\
 
\

\
3. Check the hydraulic circuit for leakage. 

BR±190
 \
 \
4. Speed Sensor Circuit. 
 \
 \
5. Park/neutral position switch circuit. 
 




TRAC indicator light
abnormal.\
 
\


\

\

1. TRAC Indicator Light Circuit.
2. TRAC ECU. 




BR±224
 


TRAC OFF indicator
light abnormal.\
 
\

\

Only when 1. and 2. are all normal and the problem is still occurring, r\
e-
place the TRAC ECU. 


BR±222
 \
 \
1. TRAC OFF indicator Light Circuit. 
 \
 \
2. TRAC cut switch circuit. 
 








Diagnostic trouble
code check cannot
be performed.\
 
\


\


\


\

\

Only when 1. and 2. are all normal and the problem is still occurring, r\
e-
place the TRAC ECU.
1. TRAC Indicator Light Circuit.
2. Tc terminal Circuit. 








BR±224
BR±226
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±173
WhereEverybodyKnowsYourName

WIRING DIAGRAM
DTC25, 26, 27TRAC Sub±Throttle Valve
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble 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 truck or operation is
faulty).

Sub±throttle position sensor.

Open or short in sub±throttle position sensor circuit.

ECM

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

Sub±throttle actuator.

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

Sub±throttle position sensor.

Open or short in sub±throttle position sensor circuit.

ECM

TRAC ECU
27When input voltage at ECU terminal VSH is less than
the specification by about 2.5 V for 0.2 sec. or more.

Sub±throttle actuator (return spring is disconnected).

Sub±throttle position sensor.

Open or short in sub±throttle position sensor circuit.

ECM

TRAC ECU
C
OK
Hint
PRemove air cleaner and duct.
Open and close the sub±throttle valve manually and
check the condition during operation.
The valve should operate smoothly without catch-
ing.
If sub±throttle actuator, sub±throttle valve, sub±throttle
position sensor and harness are free from any defect,
ECM may be defective. If ECM is free from any defect,
TRAC ECU may be defective.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±189
WhereEverybodyKnowsYourName

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 mag-
netic 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
DTC31, 32,
33, 34Speed Sensor Circuit
CIRCUIT DESCRIPTION
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 be-
tween switching the ignition switch ON and switch-
ing 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
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 E\
CU prohibits TRAC control.
BR±190
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
WhereEverybodyKnowsYourName

DTC45, 46Main Throttle Position Sensor Circuit
CIRCUIT DESCRIPTION
This circuit is not directly related to the TRAC control, but as it has an i\
nfluence on TRAC control when trouble
occurs in this circuit, it is used to switch off the TRAC system as a fail safe function.
DTC No.DTC Detecting ConditionTrouble Area
45
Either of the following (1) and (2) continues for 0.12
sec.:
(1) IDL switch of main throttle position sensoris ON.
(2) Input voltage of TRAC ECU terminal VTH:1.45 V or
more.
Main throttle position sensor

Open in VTH circuit

Short in IDL1 circuit

ECM

TRAC ECU
46
Either of the following (1) or (2) continues for0.12 sec.:
(1) Input voltage of TRAC ECU terminal VTH:4.3 V or
more.
(2) Input voltage of TRAC ECU terminal VTHwhile
IDL1 switch is OFF: 0.2 V or less
Main throttle position sensor

Short in VTH circuit

ECM

TRAC ECU
BR±200±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
WhereEverybodyKnowsYourName

OKNG
NGOK
6Check for open and short in harness and connector between terminal VTA1 of ECM and main
throttle position sensor (See page IN±33
).
Repair or replace harness or connector.
Adjust or replace main throttle position sensor
(See page EG±333 or EG±205 ).
7Check voltage between terminal IDL1 of TRAC ECU and body ground.
C
OK
PTurn ignition switch on.
Measure voltage between terminal IDL1 of TRAC ECU
and body ground, when the main throttle valve is fully
closed and fully opened.
Check and replace TRAC ECU.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±205
WhereEverybodyKnowsYourName

OKNG
10Check main throttle position sensor (See page EG±609 or EG±389 ).
Adjust or replace main throttle position sensor (See
page EG±333 or EG±205).
Check and replace ECM.
±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)BR±207
WhereEverybodyKnowsYourName

DTC47, 48Sub±Throttle Position Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the opening angle of the sub±throttle valve and sends the appropriate signals to the ECU.
If a trouble signal is input, the ECU prohibits TRAC control.
DTC No.DTC Detecting ConditionTrouble Area
47
When any of the following (1) through (3) is detected:
(1) Deviation of 5 steps or more to the closedside of the idle step during sub±throttleinitial check.
(2) Voltage at terminal IDL2 switch is OFF evenafter sub±throttle is driven to fully closedposition during
sub±throttle initial check 4.
(3) Voltage at terminal VSH is 1.45 V or morefor at least 0.15 sec. while idle switch is ON.

Sub±throttle position sensor

Open or short in IDL2 circuit

ECM

TRAC ECU
48
Either of the following (1) or (2) continues for atleast
0.12 sec.
(1) Input voltage of TRAC ECU terminal VSH:4.3 V or more.
(2) Input voltage of TRAC ECU terminal VSHis 0.2 V or less while IDL2 switch OFF.

Sub±throttle position sensor

Open or short in VSH circuit

ECM

TRAC ECU
BR±208±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
WhereEverybodyKnowsYourName