LEXUS LS430 2003 Factory Repair Manual

Fig. 98: Pedal Condition Reference Table
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: Go to step 6
HINT:
Check the stop lamp bulb as it may have burnt out.
OK:
2.INSPECT MULTIPLEX COMMUNICATION SYSTEM (SEE HOW TO PROCEED WITH
TROUBLESHOOTING )
a. Is DTC output Multiplex communication system?
Result:
DTC OUTPUT DESCRIPTION
B: REPAIR MULTIPLEX COMMUNICATION SYSTEM
A: Go to next step
3.CHECK HARNESS AND CONNECTOR (STP1 TERMINAL VOLTAGE OF DRIVER SIDE J/B
ECU)
a. Disconnect the driver side J/B ECU connector.
b. Measure the voltage according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION
DTC is not outputA
TDC is outputB
Tester ConnectionSwitch ConditionSpecified Condition
D3-13 (STP1) - Body ground Brakepedal depressed8 to 14 V
D3-13 (STP1) - Body groundBrake pedal releasedBelow 1 V

Fig. 99: Identifying Driver Side J/B ECU connector Terminals
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR
OK: Go to next step
4.CHECK HARNESS AND CONNECTOR (STPA OF DRIVER SIDE J/B ECU - STP OF SKID
CONTROL ECU)
a. Disconnect driver side J/B ECU connector and skid control ECU connector.

b. Measure the resistance according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION
Standard:
TESTER CONNECTION SPECIFIED CONDITION
Tester ConnectionSpecified Condition
D5-3 (STPA) - S42-27 (STP)Below 1 ohms
Tester ConnectionSpecified Condition
S42-27 (STP) - Body ground1 Mohms or higher

Fig. 100: Identifying Driver Side J/B ECU Connector And Skid Control ECU Connector Terminals
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: REPAIR OR REPLACE HARNESS OR CONNECTO
R

OK: Go to next step
5.RECONFIRM DTC
a. Clear the DTC (see DTC CHECK/CLEAR
).
b. Turn the ignition switch to the ON position.
c. Check that the same DTC is recorded (see DTC CHECK/CLEAR
).
OK:
The same DTC is recorded.
NG: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS
TABLE
OK: REPLACE ABS & TRACTION ACTUATOR ASSY (SEE REPLACEMENT
)
6.INSPECT STOP LAMP SWITCH ASSY
a. Disconnect the stop lamp switch assy connector.
b. Measure the resistance according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION
Switch ConditionTester ConnectionSpecified Condition
Switch pin free1 - 2Below 1 ohms
Switch pin pushed in1 - 21 Mohms or higher

Fig. 101: Identifying Stop Lamp Switch Assy Connector Terminals
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: REPLACE STOP LAMP SWITCH ASSY
OK: Go to next step
7.CHECK HARNESS AND CONNECTOR (STOP LAMP SWITCH - DRIVER SIDE J/B ECU)
a. Disconnect the stop lamp switch connector and driver side J/B connector.
b. Measure the resistance according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION
c. Measure the resistance according to the value (s) in the table below.
Standard:
Tester ConnectionSpecified Condition
(S19-1) - D3-13 (STP-1)Below 1 ohms

TESTER CONNECTION SPECIFIED CONDITION
Tester ConnectionSpecified Condition
(S19-1) - Body ground1 Mohms or higher

Fig. 102: Identifying Stop Lamp Switch Connector And Driver Side J/B Connector Terminals
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR
OK: Go to next step
8.CHECK HARNESS AND CONNECTOR (STPA OF DRIVER SIDE J/B ECU - STP OF SKID
CONTROL ECU)
a. Disconnect the driver side J/B connector and skid control ECU connector.
b. Measure the resistance according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION
Standard:
TESTER CONNECTION SPECIFIED CONDITION
Tester ConnectionSpecified Condition
D5-3 (STPA) - S42-27 (STP)Below 1 ohms
Tester ConnectionSpecified Condition
S42-27 (STP) - Body ground1 Mohms or higher

Fig. 103: Identifying Driver Side J/B Connector And Skid Control ECU Connector Terminals
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step
9.RECONFIRM DTC
a. Clear the DTC (see DTC CHECK/CLEAR
).
b. Turn the ignition switch to the ON position.
c. Check that the same DTC is recorded (see DTC CHECK/CLEAR
).
OK:
The same DTC is recorded.
NG: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS
TABLE
OK: REPLACE ABS & TRACTION ACTUATOR ASSY (SEE REPLACEMENT
)
CIRCUIT DESCRIPTION
ABS pump motor is located inside the brake actuator. The motor is used for BA, TRAC and VSC operation.
Fig. 104: DTC C1251/51 Detection Condition And Trouble Area Description Chart

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
WIRING DIAGRAM