warning light LEXUS SC400 1991 Service Workshop Manual
[x] Cancel search | Manufacturer: LEXUS, Model Year: 1991, Model line: SC400, Model: LEXUS SC400 1991Pages: 4087, PDF Size: 75.75 MB
Page 1029 of 4087
![LEXUS SC400 1991 Service Workshop Manual
w/TRAC:
Symbols
(Terminals No.)
STD Voltage (V)\
\
\
Condition](/img/36/57051/w960_57051-1028.png "LEXUS SC400 1991 Service Workshop Manual
w/TRAC:
Symbols
(Terminals No.)
STD Voltage (V)\
\
\
Condition")
w/TRAC:
Symbols
(Terminals No.)
STD Voltage (V)\
\
\
Condition
BAT
(A25±21)
±
GND
(A25±22)
10±14\
\
\
Always
IG
(A24±24)
±
GND
(A25±22)
10±14\
\
\
IG switch ON
SR
(A24±22) ± R±
(A24±25) 8.3±14\
\
IG switch ON, ABS warning light OFF
MR
(A25±16)
±
R±
(A24±25)
Below 1.0
\
\
\
IG switch ON
TSR
(A24±1)
±
R±
(A24±25)
8.3±14
\
\
\
IG switch ON, TRAC indicator light OFF
TMR
(A24±9)
±
R±
(A24±25)
Below1.0
\
\
\
IG switch ON
SFR
(A25±1)
±
GND
(A25±2)
10±14\
\
\
IG switch ON, ABS warning light OFF
SFL
(A24±13)
±
GND
(A25±22)
10±14\
\
\
IG switch ON, ABS warning light OFF
SRR
(A24±26) ±
GND
(A25±22)
10±14\
\
IG switch ON, ABS warning light OFF
SRL
(A25±12)
±
GND
(A25±13)
10±14
\
\
\
IG switch ON, ABS warning light OFF
AST
(A24±8)
±
GND
(A25±22)
10±14
\
\
\
IG switch ON, ABS warning light OFF
SAC
(A24±12)
±
GND
(A25±22)
10±14
\
\
\
IG switch ON, TRAC indicator light OFF
SMC
(A24±2)
±
GND
(A25±22)
10±14\
\
\
IG switch ON, TRAC indicator light OFF
SRC
(A24±15)
±
GND
(A25±22)
10±14\
\
\
IG switch ON, TRAC indicator light OFF
PR
(A24±10)
±
E2
(A24±20)
5±7\
\
\
IG switch ON
VC
(A24±19) ± E2
(A24±20) 4±6\
\
IG switch ON
ALT
±
GND
Below 1.0\
\
\
IG switch ON
ALT
(A25±8)
±
GND
(A25±22) 10±14\
\
Idling
WA ± GND Below 2.0\
\
IG switch ON, ABS warning light ON
WA
(A25±9) ±
GND
(A25±22) 10±14\
\
IG switch ON, ABS warning light OFF
PKB
±
GND
Below 1.5\
\
\
IG switch ON, PKB switch ON,
Fluid in M/C reservoir above MIN level
PKB
(A25±17)
±
GND
(A25±22)
10±14\
\
\
IG switch ON, PKB switch OFF,
Fluid in M/C reservoir above MIN level
BR±60±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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Page 1030 of 4087
![LEXUS SC400 1991 Service Workshop Manual
Symbols
(Terminals No.)
STD Voltage (V)\
\
\
Condition
LBL
(A25Â](/img/36/57051/w960_57051-1029.png "LEXUS SC400 1991 Service Workshop Manual
Symbols
(Terminals No.)
STD Voltage (V)\
\
\
Condition
LBL
(A25Â")
Symbols
(Terminals No.)
STD Voltage (V)\
\
\
Condition
LBL
(A25±6) ± GND
(A25±22) 10±14\
\
IG switch ON
Fluid in M/C reservoir tank above MIN level.
STP
±
GND
Below 1.5\
\
\
Stop light switch OFF
STP
(A25±10)
±
GND
(A25±22)
8±14
\
\
\
Stop light switch ON
D/G
(A25±20) ± GND
(A25±22) 10±14\
\
IG switch ON, ABS warning light OFF
Tc
(A26±3)
±
GND
(A25±22)
10±14
\
\
\
IG switch ON
Ts
(A26±1)
±
GND
(A25±22)
10±14
\
\
\
IG switch ON
P
±
GND 10±14\
\
IG switch ON, Shift position in ªPº position P
(A26±10) ± GND
(A25±22) Below 1.5\
\
IG switch ON, Other shift position in ªPº position
N
±
GND
(A25±22)
10±14
\
\
\
IG switch ON, Shift position in ªNº position
N
(A26±5) ± (A25±22) Below 1.5\
\
IG switch ON, Other shift position in ªNº position
FR+
(A24±17)
±
FR±
(A24±4)
AC generation\
\
\
IG switch ON
Slowly turn right front wheel.
FL+
(A24±5)
±
FL±
(A24±18)
AC generation\
\
\
IG switch ON
Slowly turn left front wheel.
RR+
(A25±14)
±
RR±
(A25±3)
AC generation\
\
\
IG switch ON
Slowly turn right rear wheel.
RL+
(A25±4) ± RL±
(A25±15) AC generation\
\
IG switch ON
Slowly turn left rear wheel.
FRO
(A26±15)
±
GND
(A25±22)
Pulse generation
\
\
\
IG switch ON
Slowly turn right front wheel.
FLO
(A26±6)
±
GND
(A25±22)
Pulse generation
\
\
\
IG switch ON
Slowly turn left front wheel.
RRO
(A26±13)
±
GND
(A25±22)
Pulse generation
\
\
\
IG switch ON
Slowly turn right rear wheel.
RLO
(A26±4)
±
GND
(A25±22)
Pulse generation\
\
\
IG switch ON
Slowly turn left rear wheel.
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±61
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Page 1041 of 4087
![LEXUS SC400 1991 Service Workshop Manual
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](/img/36/57051/w960_57051-1040.png "LEXUS SC400 1991 Service Workshop Manual
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")
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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Page 1045 of 4087
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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Page 1046 of 4087
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 CLEARANCE
1. Using SST, connect terminals Tc and E1 of DLC2 or DLC1. SST 09843±18020
2. IG switch ON.
3. Clear the diagnostic trouble codes stored in ECU by depressing the brake pedal 8 or more times within 3 seconds.
4. Check that the warning light shows the normal code.
5. Remove the SST from the terminals of DLC2 or DLC1.
6. Connect the Short Pin to DLC1.
HINT: Cancellation can also be done by removing the DOME
fuse, but in this case, other memory systems will also be can-
celled out.
ECU TERMINAL VALUES MEASUREMENT USING LEXUS BREAK±OUT±BOX AND LEXUS HANDHELD TESTER
1. Hook up the LEXUS hand±held tester and LEXUS
break±out±box to the vehicle.
2. Read the ECU input/output values by following the prompts on the scan tool screen.
HINT: LEXUS hand±held tester has a ªSnapshotº function.
This records the measured values and is effective in the diag-
nosis of intermittent problems.
Please refer to the LEXUS hand±held tester/LEXUS break±
out±box operator's manual for further details.
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±77
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Page 1049 of 4087
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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Page 1051 of 4087
![LEXUS SC400 1991 Service Workshop Manual
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 tab](/img/36/57051/w960_57051-1050.png "LEXUS SC400 1991 Service Workshop Manual
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 tab")
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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Page 1102 of 4087
OKNG
OKNG
OKNG
INSPECTION PROCEDURE
1Check brake fluid level.
Check the amount of fluid in the bake reservoir.C
Check and repair brake fluid leakage and add fluid.
2Check brake fluid level warning switch.
See page BE±142.
Replace brake fluid level warning switch.
3Check for short in all the harness and components connected to brake fluid le\
vel warning light
(See page IN±33).
Repair or replace harness or connector.
Check and replace ABS & TRAC ECU.
±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)BR±133
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Page 1113 of 4087
![LEXUS SC400 1991 Service Workshop Manual
WIRING DIAGRAM
ABS Warning Light Circuit
CIRCUIT DESCRIPTION
If the ECU detects trouble, it lights the ABS warning light while at the s\
ame time prohibiting ABS control.
At this time, the ECU record](/img/36/57051/w960_57051-1112.png "LEXUS SC400 1991 Service Workshop Manual
WIRING DIAGRAM
ABS Warning Light Circuit
CIRCUIT DESCRIPTION
If the ECU detects trouble, it lights the ABS warning light while at the s\
ame time prohibiting ABS control.
At this time, the ECU record")
WIRING DIAGRAM
ABS Warning Light Circuit
CIRCUIT DESCRIPTION
If the ECU detects trouble, it lights the ABS warning light while at the s\
ame time prohibiting ABS control.
At this time, the ECU records a diagnostic trouble code in memory.After removing the short pin of the DLC1,
connect a DLC1 or connect terminals Tc and E1 of the DLC2 to make the ABS warning light to blink and
output the diagnostic trouble code.DIAGNOSTIC CHARTPerform troubleshooting in accordance with the
chart below for each trouble symptom.
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Perform troubleshooting in accordance with the chart below for each trouble sym\
ptom.
ABS warning light does not light up
Go to step
ABS warning light remains on
Go to step
BR±144±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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Page 1115 of 4087
OKNG
OKNG
INSPECTION PROCEDURE
1Check ABS warning light.
See Combination Meter Troubleshooting on page BE±159.
Replace bulb or combination meter assembly.
2Check ABS solenoid relay.
C
OK
P
OK
C
Remove solenoid relay from R/B No. 6.
Check continuity between each terminal of ABS sole-
noid relay shown below.
1. Apply battery voltage between terminals 4 and 6.
2. Check continuity between each terminal of ABS so-
lenoid relay shown below.
Replace ABS solenoid relay.
Repair or replace and check for open in harness and connector between ch\
eck connector and ABS
solenoid relay and body ground (See page IN±33).
BR±146±
BRAKE SYSTEM ANTI±LOCK BRAKE SYSTEM (ABS)
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