2003 LEXUS LS430 Ecm

Fig. 53: DTC P1631 And U0100 Problem Symptom Diagnostic Chart
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
HINT:
This circuit uses CAN for communication. Therefore, if there are any malfunctions in the communication
circuit, one or more DTCs in the CAN communication system is/are output.
1.GO TO CAN COMMUNICATION SYSTEM (SEE HOW TO PROCEED WITH
TROUBLESHOOTING )
CIRCUIT DESCRIPTION
The ABS & traction actuator assy (skid control ECU) receives the alarm demand signal from the ECM and
operates the skid control buzzer.
The buzzer sounds to warn that the distance between the vehicle in front and your own vehicle is shortening.
Fig. 54: DTC P1575 Problem Symptom Diagnostic
Chart
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
HINT:
If the vehicle ahead in the same lane significantly decreases its speed or another vehicle pulls in front of your
own vehicle, adequate deceleration cannot be applied and the vehicle-to-vehicle distance will shorten. At this
time, the s
ystem sounds the buzzer and the master warning light blinks to inform the driver.

This circuit uses CAN for communication. Therefore, if there are any malfunctions in the communication
circuit, one or more DTCs in the CAN communication system is/are output.
WIRING DIAGRAM
See WIRING DIAGRAM
.
INSPECTION PROCEDURE
See INSPECTION PROCEDURE
.
CIRCUIT DESCRIPTION
This DTC is output when the VSC system has a problem. Check the VSC system when this DTC is output.
DTC P1578 PROBLEM SYMPTOM DIAGNOSTIC
INSPECTION PROCEDURE
HINT:
This circuit uses CAN for communication. Therefore, if there are any malfunctions in the communication
circuit, one or more DTCs in the CAN communication system is/are output.
1.CHECK BRAKE SYSTEM (SEE HOW TO PROCEED WITH TROUBLESHOOTING
)
CIRCUIT DESCRIPTION
The laser sensor and cruise control ECU (distance control ECU) transmit the data for general vehicle control
and diagnosis function along the communication line.
The laser sensor transmits information about the vehicle in front to the cruise control ECU (distance control
ECU).
DTC No.DTC Detection ConditionTrouble Area
P1578This trouble code is output when the ECM receives the brake
system error signal for 0.2 sec. or more while the dynamic laser
cruise control is in operation.VSC system

Fig. 66: Signal Waveform Graph
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
OK: REPLACE LASER SENSOR (SEE REPLACEMENT
)
CIRCUIT DESCRIPTION
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 on object in front. This data is transmitted to the cruise control ECU (distance
control ECU).
DTC P1570 PROBLEM SYMPTOM DIAGNOSTIC
HINT:
DTC No.Detection ItemTrouble Area
P1570The ECM outputs this trouble code when it detects the communication
error signal (from the cruise control ECU (distance control ECU) to the
laser sensor) for 0.15 sec. or more while the dynamic laser cruise control
is in operation.laser sensor

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.).
INSPECTION PROCEDURE
1.ADJUST LASER SENSOR (SEE ADJUSTMENT
)
HINT:
It is necessary to make the ECM recognize spec information (whether the vehicle is equipped with the
dynamic laser or not). When this procedure has not been carried out, this DTC may be output.
1. Clear the DTC and then recheck for DTCs.
OK: DTC is not output.
HINT:
If DTC P1570 is still output after performing the above procedures, replace the laser sensor.
NG: REPLACE LASER SENSOR (SEE REPLACEMENT
)
OK: SYSTEM OK
CIRCUIT DESCRIPTION
This DTC is output when the scanning angle of the laser sensor is incorrect.
This DTC is also output when the laser sensor optical axis is in an incorrect position is detected.
DTC P1572 PROBLEM SYMPTOM DIAGNOSTIC

HINT:
If the optical axis deviates to the upper/lower side +/-2° or more and/or the right/left side +/-4° or more, this
DTC is detected.
INSPECTION PROCEDURE
1.ADJUST LASER SENSOR (SEE ADJUSTMENT
)
CIRCUIT DESCRIPTION
This circuit detects the angle and direction of steering and automatically transmits its signal to the skid control
ECU and distance control ECU.
Fig. 67: DTC U0126 Problem Symptom Diagnostic Chart

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
HINT:
This circuit uses CAN for communication. Therefore, if there are any malfunctions in the communication
circuit, one or more DTCs in the CAN communication system is/are output.
1.GO TO CAN COMMUNICATION SYSTEM (SEE HOW TO PROCEED WITH
TROUBLESHOOTING )
CIRCUIT DESCRIPTION
DTC
No.DTC Detection ConditionTrouble
Area
P1572
The ECM outputs this trouble code when the ECU detects that the laser sensor optical
axis is in an incorrect position (0.15 sec. or more) while dynamic laser cruise control
is in operation.laser
sensor

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. 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

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