2003 LEXUS LS430 ECU

CIRCUIT DESCRIPTION
The speed sensor detects wheel speed and sends the appropriate signals to the ECU. These signals are used to
control the ABS control system. The front and rear rotors have 48 serrations respectively.
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 direct proportion to the speed of the rotor, the
frequenc
y is used by the ECU to detect the speed of each wheel.

OK: Go to next step
3.INSPECT SPEED SENSOR AND SENSOR ROTOR SERRATIONS
INSPECTION USING OSCILLOSCOPE
a. Connect the oscilloscope to terminal FR+ - FR- or FL+ - FL- of the skid control ECU.
b. Drive the vehicle at approximately 19 mph (30 km/h), and check the signal waveform.
OK: Go to next step
A waveform as shown in a figure should be output.
HINT:
As the vehicle speed (wheel revolution speed) increases, a cycle of the waveform narrows and the
fluctuation in the output voltage becomes greater.
When noise is identified in the waveform on the oscilloscope, error signals are generated due to the
speed sensor rotor's scratches, looseness or foreign matter attached to it.
NG: Go to step 7

Standard:
TESTER CONNECTION SPECIFIED CONDITION LH:
TESTER CONNECTION SPECIFIED CONDITION RH:
FRONT SPEED SENSOR SUB-WIRE HARNESS
a. Remove the front fender liner.
b. Make sure that the speed sensor connector and the wire harness side connector are securely
connected.
c. Disconnect the speed sensor connector inside the vehicle.
d. Measure the resistance according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION LH:
TESTER CONNECTION SPECIFIED CONDITION RH:
e. Measure the resistance according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION LH:
TESTER CONNECTION SPECIFIED CONDITION RH:
Tester ConnectionSpecified Condition
A8-2 (FL+) - Body ground1 Mohms or higher
A8-1 (FL-) - Body ground1 Mohms or higher
Tester ConnectionSpecified Condition
A7-2 (FR+) - Body ground1 Mohms or higher
A7-1 (FR-) - Body ground1 Mohms or higher
Tester ConnectionSpecified Condition
(Connector A-1) - (Connector B-1)Below 1 ohms
(Connector A-2) - (Connector B-2)Below 1 ohms
Tester ConnectionSpecified Condition
(Connector A-1) - (Connector B-1)Below 1 ohms
(Connector A-2) - (Connector B-2)Below 1 ohms
Tester ConnectionSpecified Condition
(Connector A-1) - (Connector A-2)1 Mohms or higher
Tester ConnectionSpecified Condition
(Connector A-1) - (Connector A-2)1 Mohms or higher

Fig. 49: Identifying Speed Sensor Connector And Wire Harness Side Connector Terminals
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
OK: Go to next step
5.CHECK HARNESS AND CONNECTOR (FRONT SPEED SENSOR - SKID CONTROL ECU)
Fig. 50: Identifying Skid Control ECU Connector And Front Speed Sensor Connector Terminals

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
a. Disconnect the skid control ECU connector and the front speed sensor connector.

b. Measure the resistance according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION LH:
TESTER CONNECTION SPECIFIED CONDITION RH:
c. Measure the resistance according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION LH:
TESTER CONNECTION SPECIFIED CONDITION RH:
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR
OK: Go to next step
6.INSPECT SPEED SENSOR AND SENSOR ROTOR SERRATIONS
INSPECTION USING OSCILLOSCOPE
a. Connect the oscilloscope to terminal FR+ - FR- or FL+ - FL- of the skid control ECU.
b. Drive the vehicle at approximately 19 mph (30 km/h), and check the signal waveform.
OK: Go to next step
A waveform as shown in a figure should be output.
HINT:
Tester ConnectionSpecified Condition
S42-18 (FL+) - A8-2 (FL+)Below 1 ohms
S42-4 (FL-) - A8-1 (FL-)Below 1 ohms
Tester ConnectionSpecified Condition
S42-3 (FR+) - A7-2 (FR+)Below 1 ohms
S42-17 (FR-) - A7-1 (FR-)Below 1 ohms
Tester ConnectionSpecified Condition
S42-18 (FL+) - Body ground1 Mohms or higher
S42-4 (FL-) - Body ground1 Mohms or higher
Tester ConnectionSpecified Condition
S42-3 (FR+) - Body ground1 Mohms or higher
S42-17 (FR-) - Body ground1 Mohms or higher

NG: Go to step 4
OK: Go to next step
3.INSPECT SPEED SENSOR AND SENSOR ROTOR SERRATIONS
Fig. 55: Normal Signal Waveform

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION USING OSCILLOSCOPE
a. Connect the oscilloscope to terminals RR+ - RR- or RL+ - RL- of the skid control ECU.
b. Drive the vehicle at approximately 19 mph (30 km/h), and check the signal waveform.
OK: Go to next step
A waveform as shown in a figure should be output.
HINT:
As the vehicle speed (wheel revolution speed) increases, a cycle of the waveform narrows and the

fluctuation in the output voltage becomes greater.
When noise is identified in the waveform on the oscilloscope, error signals are generated due to the
speed sensor rotor's scratches, looseness or foreign matter attached to it.
NG: Go to step 7
OK: REPLACE ABS & TRACTION ACTUATOR ASSY (SEE REPLACEMENT
)
4.INSPECT REAR SPEED SENSOR
Fig. 56: Inspecting Rear Speed Sensor

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
a. Remove the rear seat cushion and seatback.
b. Make sure that the speed sensor connector and the wire harness side connector are securely
connected.
c. Disconnect the speed sensor connector.
d. Measure the resistance accordin
g to the value (s) in the table below.

Standard:
TESTER CONNECTION SPECIFIED CONDITION LH:
TESTER CONNECTION SPECIFIED CONDITION RH:
e. Measure the resistance according to the value (s) in the table below.
Standard:
TESTER CONNECTION SPECIFIED CONDITION LH:
TESTER CONNECTION SPECIFIED CONDITION RH:
NG: REPLACE REAR SPEED SENSOR (SEE REPLACEMENT
)
OK: Go to next step
5.CHECK HARNESS AND CONNECTOR (REAR SPEED SENSOR - SKID CONTROL ECU)
Tester ConnectionSpecified Condition
(A31-1) - (A31-2)0.6 to 1.8 kohms
Tester ConnectionSpecified Condition
(A30-1) - (A30-2)0.6 to 1.8 kohms
Tester ConnectionSpecified Condition
(A31-1) - Body ground1 Mohms or higher
(A31-2) - Body ground1 Mohms or higher
Tester ConnectionSpecified Condition
(A30-1) - Body ground1 Mohms or higher
(A30-2) - Body ground1 Mohms or higher