1991 LEXUS SC300 display

BR±160).
IN±33 ).
WIRING DIAGRAM
Tc Terminal Circuit
CIRCUIT DESCRIPTION
By connecting between terminals Tc and E1 of DLC1 or DLC2, the ECU displays the diagnostic trouble
code by blinking the TRAC indicator light.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±226±
BRAKE SYSTEM TRACTION CONTROL SYSTEM (TRAC)
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DIAGNOSIS SYSTEM
INDICATOR CHECKWhen the ignition switch is turned on, check that the ABS
warning light goes on for 3 seconds.
HINT: If the indicator check result is not normal, proceed to
trouble shooting for the ABS warning light circuit (see page
BR±144 ).
DIAGNOSTIC TROUBLE CODE CHECK
1. Turn the ignition switch to ON.
2. Disconnect the Short Pin from DLC1.
3. Using SST, connect terminals Tc and E1 of DLC2 or DLC1. SST 09843±18020
4. Read the diagnostic trouble code from the ABS warning light
on the combination meter.
HINT: If no code appears, inspect the diagnostic circuit or
ABS warning light circuit (See page BR±148 or BR±144 ).
As an example, the blinking patterns for normal code and
codes 11 and 21 are shown on the left.
5. Codes are explained in the code table on page BR±78.
6. After completing the check, disconnect terminals Tc and E1, and turn off the display.
If 2 or more malfunctions are indicated at the same time, the
lowest numbered diagnostic trouble code will be displayed
first.
BR±76
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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DIAGNOSTIC TROUBLE CODE CHART
If a malfunction code is displayed during the diagnostic trouble code chec\
k, check the circuit listed for that
code, in the table below and proceed to the relevant page.
HINT: Using SST 09843±18020, connect the terminals Tc and E1, and remove the short pin.
BR±94BR±98
BR±102
BR±106BR±110
BR±114
BR±118 BR±94
BR±98
BR±102
BR±106
BR±110BR±110
BR±110
BR±114
BR±114
BR±118
BR±118
BR±118
BR±78
±
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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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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IN±33).
WIRING DIAGRAM
Tc Terminal Circuit
CIRCUIT DESCRIPTION
Connecting between terminals Tc and E1 of the DLC1 or the DLC2 causes the ECU to display the diagnos-
tic trouble code by flashing the ABS warning light.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
BR±148±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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HOW TO PROCEED WITH TROUBLESHOOTING
The Engine Control System broadly consists of the sensors, ECU and actuator\
s. The ECU receives signals from
various sensors, judges the operating conditions and determines the opti\
mum injection duration, timing, ignition
timing and idle speed.
In general, the Engine Control System is considered to be a very intricate\
system to troubleshoot. But, the fact
is that if you proceed to inspect the circuit one by one following the p\
rocedures directed in this manual, trouble-
shooting of this system is not complex.
This section explains the most ideal method of troubleshooting and tells how\
to carry out the necessary repairs.
[1] CUSTOMER PROBLEM ANALYSISUsing the customer problem analysis check sheet for reference, ask the c\
ustomer in as much details as
possible about the problem.
[2] CHECK AND CLEAR DIAGNOSTIC CODE (PRECHECK) Before confirming the problem symptom, first check the diagnostic code and mak\
e a note of any malfunc-
tion code which is output, then clear the code.
HINT: Output of the malfunction code indicates that there is a malfunction in\
the circuit indicated. However,
it does not indicate whether the malfunction is still occurring or occur\
red in the past and returned to normal.
In order to determine this, the problem symptoms should be confirmed in 4 \
first and the diagnostic code
be rechecked in [6].
Accordingly, if troubleshooting is begun based on the malfunction code only in diag\
nostic code check in
[2] , it could result in a misdiagnosis, leading to troubleshooting of circuits which are normal \
and making
it more difficult to locate the cause of the problem.
[3] SETTING THE TEST MODE DIAGNOSIS, [4] PROBLEM SYMPTOM CONFIRMATION, [5] SYMPTOM SIMULATION
In order to find out the trouble more quickly, set the diagnosis check in test mode and with higher sensing
ability of the ECU, confirm the problem symptoms. If the trouble does not reappear, use the symptom simu-
lation method to make sure the trouble is reproduced.
[6] DIAGNOSTIC CODE CHECK IN TEST MODE Check the diagnostic code in test mode. If the malfunction code is output, pr\
oceed to ºstep [8] Diagnostic
Code Chartº. If the normal code is output, proceed to ºstep [7] Basic Inspectionº.
[7] BASIC INSPECTION Carry out basic inspection such as the spark check and fuel pressure che\
ck, etc.
[8] DIAGNOSTIC CODE CHART If the malfunction code is displayed, proceed to inspect the circuit ind\
icated by the chart for each code.
[9] MATRIX CHART OF PROBLEM SYMPTOMS If the normal code is displayed in the diagnosis in test mode, perform tro\
ubleshooting according to the in-
spection order in the Matrix Chart of Problem Symptoms.
[10] PARTS INSPECTION When the Matrix Chart of Problem Symptoms instructs to check the parts, proc\
eed to parts inspection sec-
tion included in this manual.
[11] CIRCUIT INSPECTION Determine if the malfunction is the sensor, actuator, wire harness, connector or the ECU.
TR±2
±
ENGINE TROUBLESHOOTING How to Proceed with Troubleshooting
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How to Proceed with Troubleshooting Using Volt/Ohm Meter
and TCCS Checker
For the explanation of steps [1] ~ [6], [8] and [10] ~ [16], see the explan\
ation of steps with the same title on page
TR±2.
[7] [9] CIRCUIT INSPECTION BY CHECKER If the Normal code is displayed in the diagnostic code check, connect the \
checker to the vehicle and check
all the circuits which can be inspected using the checker.
If a malfunctioning circuit is then detected, proceed to ºCircuit Ins\
pection by Volt/Ohm Meterº and check
the applicable circuit using a volt/ohm meter. Determine if the malfunction is in the sensor, actuator, wire
harness, connector or the ECU. If the malfunctioning circuit cannot be detected u\
sing the checker, proceed
to ºBasic Inspectionº and perform troubleshooting.
If a malfunction code is displayed in the diagnostic code check, use the c\
hecker to inspect the circuit indi-
cated by the diagnostic code chart for the displayed code.
For instructions on how to connect the checker to the vehicle and how to us\
e the checker, please refer to
the Instruction Manual for TCCS checker.
TR±6
±
ENGINE TROUBLESHOOTING How to Proceed with Troubleshooting
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