LEXUS LS430 2003 Factory Repair Manual

Fig. 69: Wiring Diagram - Distance Control ECU Power Source Circuit
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
1.INSPECT CRUISE CONTROL ECU ASSY (DISTANCE CONTROL ECU)
a. Disconnect the cruise control ECU (distance control ECU) connector.
b. Measure the voltage according to the value(s) in the table below.
Standard:
CRUISE CONTROL ECU VOLTAGE RESISTANCE SPECIFICATION

c. Measure the resistance according to the value(s) in the table below.
Standard:
CRUISE CONTROL ECU TERMINALS RESISTANCE SPECIFICATION
NG: REPAIR OR REPLACE WIRE HARNESS OR CONNECTOR
Fig. 70: Disconnecting Cruise Control ECU (Distance Control ECU) Connector

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
OK: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS
TABLE
Tester connectionConditionSpecified value
D2-1 (+B) - Body groundIgnition SW ON10 to 14 V
Tester connectionConditionSpecified value
D2-10 (SGND) - Body groundAlwaysBelow 1 ohms
D2-12 (GND) - Body groundAlwaysBelow 1 ohms

CIRCUIT DESCRIPTION
This circuit provides power to operate the laser sensor.
The laser sensor emits laser beams towards an object in front and measures the distance and direction of the
object by receiving the beam reflections. Based on the reflections, the sensor calculates the difference in speed
between your own vehicle and an object in front. This data is transmitted to the cruise control ECU (distance
control ECU).
HINT:
The laser sensor monitors the laser emission and reception by itself. This DTC is detected when it cannot
monitor.
When rain drops or snowflakes strike the laser sensor face, the distance between the vehicle in front and your
own vehicle cannot be measured correctly.
The dynamic laser cruise control system functions by detecting the reflector of the vehicle directly in front. In
the following cases, the system may not be able to detect the vehicle in front and may not properly maintain the
correct vehicle-to-vehicle distance.
The vehicle in front is a tall trailer.
The back of the vehicle in front is extremely dirty.
Emissions from the vehicle in front or from other lanes are heavy.
The vehicle in front has no reflector.
The laser sensor is receiving a strong flash of light (sunlight, etc.).
WIRING DIAGRAM

Fig. 71: Wiring Diagram - Laser Sensor Power Source Circuit
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
1.INSPECT LASER SENSOR
a. Disconnect the laser sensor connector.
b. Measure the voltage according to the value(s) in the table below.
Standard:
LASER SENSOR CONNECTOR TERMINALS VOLTAGE SPECIFICATION
Tester connectionConditionSpecified value
L1-5 (IGB) - Body groundIgnition SW ON10 to 14 V

Fig. 72: Disconnecting Laser Sensor Connector
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: Go to step 3
OK: Go To Next Step.
2.CHECK WIRE HARNESS AND CONNECTOR
a. Disconnect the ECM E3 connector.
b. Measure the resistance according to the value(s) in the table below.
Standard:
ECM CONNECTOR TERMINALS RESISTANCE SPECIFICATION
Tester connectionConditionSpecified value
L1-1 (LGND) - E3-29 (LGND)AlwaysBelow 1 ohms
L1-1 (LGND) - Body groundAlways10 kohms or higher
L1-2(SGND) - Body groundAlwaysBelow 1 ohms

Fig. 73: Disconnecting Laser Sensor Connector
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Fig. 74: Disconnecting ECM E3 Connector
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: REPAIR OR REPLACE WIRE HARNESS OR CONNECTOR
OK: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS
TABLE
3.CHECK WIRE HARNESS AND CONNECTOR (LASER SENSOR - DISTANCE CONTROL
ECU)
a. Disconnect the cruise control ECU (distance control ECU) connector.
b. Measure the resistance according to the value(s) in the table below.
Standard:
LASER SENSOR AND DISTANCE CONTROL ECU TERMINALS RESISTANCE
SPECIFICATION
Tester connectionConditionSpecified value
D2-13 (IGB) - L1-5 (IGB)AlwaysBelow 1 ohms
D2-13 (IGB) - Body groundAlways10 kohms or higher

Fig. 75: Disconnecting Laser Sensor Connector
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
Fig. 76: Disconnecting Cruise Control ECU (Distance Control ECU) Connector

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: REPAIR OR REPLACE WIRE HARNESS OR CONNECTOR
OK: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS
TABLE
CIRCUIT DESCRIPTION
The cruise control main switch operates eight functions: SET, COAST, TAP-DOWN, RESUME, ACCEL,
TAP-UP, CANCEL and MODE. The SET, TAP-DOWN and COAST functions, and the RESUME, TAP-UP
and ACCEL functions are operated with the same switch. The cruise control main switch is an automatic return
type switch which turns on only while operating it in each arrow direction and turns off after releasing it. The

internal contact point of the cruise control main switch is turned on with the switch operation. The ECM then
reads the resistance value that has been changed by the switch operation to control MODE, SET, COAST,
RESUME, ACCEL and CANCEL.
The dynamic laser cruise control system has two cruise control modes: the constant speed control mode and
vehicle-to-vehicle distance control mode.
The vehicle-to-vehicle distance control mode is always selected when starting up the dynamic laser cruise
control system.
The operation of the constant speed control mode is the same as that for the conventional type cruise
control system.
WIRING DIAGRAM
Fig. 77: Wiring Diagram
- Cruise Control Switch Circuit
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
1.READ VALUE OF HAND-HELD TESTER