2003 LEXUS LS430 cruise control

OK: REPLACE DRIVER SIDE J/B
CIRCUIT DESCRIPTION
This DTC indicates a malfunction in the ECM.
HINT:
The ECM receives signals from each sensor to control all the functions of the cruise control with the
microcomputer.
When a malfunction is detected, fail-safe remains on until the ignition switch is turned off.
DTC P0607 PROBLEM SYMPTOM DIAGNOSTIC
INSPECTION PROCEDURE
1.REPLACE ECM (SEE REPLACEMENT
)
CIRCUIT DESCRIPTION
The distance control ECU receives information about the area in front of the vehicle from the laser sensor and
then sends a brake control demand signal (deceleration demand) and diagnosis signals, such as laser sensor
grime or laser sensor malfunction, to the ECM.
DTC No.Detection ItemTrouble Area
P0607The ECM has a supervisory CPU and a control ECU inside. When each
input STP signal is different for 0.15 sec. or more, this trouble code is
output. This trouble code is output after 0.4 sec. has passed from the time
the cruise cancel input signal (STP input) is input into the ECM.ECM

Fig. 50: DTC P1615 And U1101 Problem Symptom Diagnostic Chart
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
HINT:
This circuit uses CAN for communication. Therefore, one or more DTCs in the CAN communication system
is/are output if there are any malfunctions in the communication circuit.
1.GO TO CAN COMMUNICATION SYSTEM (SEE HOW TO PROCEED WITH
TROUBLESHOOTING )
CIRCUIT DESCRIPTION
The ECM receives signals from each sensor and ECU, then sends signals such as the A/T signal, cruise control
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480003004600520051005700550052004f0003005200530048[ration signal and laser light emission prohibiting
signal, etc. to the distance control ECU.
<0037004b004800030028002600300003004c005600030057004b0048000300520051004f005c000300460052005000530052005100480051005700030057004b004400570003004b0044005600030044000300490058005100460057004c00520051000300
57005200030055004800460052005500470003004400510047[ output the DTCs in the dynamic laser cruise
control system. Therefore if the distance control ECU detects a communication error from the ECM, it sends the
malfunction signal back to the ECM.
Fig. 51: DTC P1616 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
In the dynamic laser cruise control system, the ECM and the distance control ECU communicate with one
another to control the system based on some designation information. If the designation information of the
ECM and distance control ECU is different from each other, this DTC is recorded.
DTC P1617 PROBLEM SYMPTOM DIAGNOSTIC
INSPECTION PROCEDURE
1.CONFIRM THE DESIGNATION INFORMATION
a. If this DTC is output, confirm the designation information by following the procedures below.
1. Turn the ignition switch to the ON position.
2. Push the ON-OFF button of the cruise main switch on.
3. With the brake pedal depressed, push the cruise control main switch to RES/ACC 3 times
within 3 seconds. Check that the VSC buzzer sounds at this time.
If the light control switch is turned on by mistake, readjust the optical axis (refer to
ADJUSTMENT
for optical axis adjustment).
4. Clear the DTC and then recheck for DTCs.
OK: DTC is not output.
HINT:
If DTC P1617 is still output after performing the above procedures, replace the distance control ECU.
If the DTC P1617 is still output after replacing the distance control ECU, replace the ECM.
DTC No.DTC Detecting ConditionTrouble Area
P1617While the dynamic laser cruise control is either
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5100440057004c005200510003[
signal from the ECM and the designation return signal
from the distance control ECU do not match one another
for a certain amount of time or more, the ECM records
this trouble code.Cruise control ECU
(Distance control ECU)

NG: REPLACE CRUISE CONTROL ECU ASSY (SEE REPLACEMENT )
OK: SYSTEM OK
CIRCUIT DESCRIPTION
The skid control ECU sends signals such as cruise control cancel demand signal, brake operation demand
response signal from the ECM, etc. to the ECM when the dynamic laser cruise control system is in operation.
Fig. 52: DTC P1630 And U0122 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 ECM sends signals such as A/T information signal, dynamic laser cruise control operation signal, brake
operation demand signal, buzzer operation demand signal and low speed mode signal, etc. to the skid control
ECU when the dynamic laser cruise control is in operation.
<0037004b004800030028002600300003004c005600030057004b0048000300520051004f005c000300460052005000530052005100480051005700030057004b004400570003004b0044005600030044000300490058005100460057004c00520051000300
57005200030055004800460052005500470003004400510047[ output the DTCs in the dynamic laser cruise
control system. Therefore if the skid control ECU detects a communication error from the ECM, it sends the
malfunction signal back to the ECM.

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. 55: DTC U0235 Problem Symptom Diagnostic Chart
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
WIRING DIAGRAM
Fig. 56: Wiring Diagram
- Lost Communication With Cruise Control Front Distance Range Sensor
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
1.CHECK WIRE HARNESS AND CONNECTOR (DISTANCE CONTROL ECU - LASER
SENSOR)
a. Disconnect the distance control ECU and laser sensor connectors.
b. Measure the resistance according to the value(s) in the table below.
Standard:
DISTANCE CONTROL ECU AND LASER SENSOR CONNECTOR TERMINALS
RESISTANCE SPECIFICATION
Tester connectionConditionSpecified value
D2-22 (LRDD) - L1-3 (LRDD)AlwaysBelow 1 ohms
D2-13 (IGB) - L1-5 (IGB)AlwaysBelow 1 ohms
D2-22 (LRDD) - Body groundAlways10 kohms or higher
D2-13 (IGB) - Body groundAlways10 kohms or higher

Fig. 60: Signal Waveform Graph
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
OK: REPLACE CRUISE CONTROL ECU ASSY (SEE REPLACEMENT
)
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 cruise control ECU (distance control ECU) determines the presumed R information based on the signal
from the steering wheel and yaw rate sensor.
The cruise control ECU (distance control ECU) transmits the current vehicle speed and presumed R information
to the laser sensor.

Fig. 64: Disconnecting Laser Sensor Connector
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: REPAIR OR REPLACE WIRE HARNESS OR CONNECTOR
OK: Go To Next Step.
2.INSPECT CRUISE CONTROL ECU ASSY (DISTANCE CONTROL ECU)
a. Reconnect the cruise control ECU (distance control ECU) connector.
b. Turn the ignition switch to the ON position.
c. Measure the voltage according to the value(s) in the table below.
Standard:
CRUISE CONTROL ECU TERMINALS VOLTAGE SPECIFICATION
Tester connectionConditionSpecified value
D2-13 (IGB) - Body groundIgnition SW ON10 to 14 V