2003 LEXUS LS430 Ecm

a. Connect the hand-held tester to the DLC3.
b. Turn the ignition switch to the ON position.
c. According to the display on the tester, perform the "ACTIVE TEST".
HINT:
The ignition switch must be turned to the ON position to proceed to the ACTIVE TEST using the hand-
held tester.
COMBINATION METER ASSY:
ACTIVE TEST DETAIL (COMBINATION METER ASSY)
HINT:
If a trouble code is displayed during the DTC check, check the circuit listed for that code. For details of each
code, refer to the DTC chart below.
DIAGNOSTIC TROUBLE CODE CHART
ItemVehicle Condition / Test DetailsDiagnostic Note
CRUISE INDIC"CRUISE" indicator is ON / OFF-
L-CRUISE DISPGraphic area is ON / OFF((1))
L-CRS CHECK IND"CHECK CRUISE SYSTEM" indicator is
ON / OFF-
L-CRS READY IND"RADAR READY" indicator is ON / OFF-
(1)The entire graphic area in the combination meter will light up.
DTCDescription
DTC P0500, DTC P0503VEHICLE SPEED SENSOR CIRCUIT MALFUNCTION
DTC P0571STOP LIGHT SWITCH CIRCUIT MALFUNCTION
DTC P0607INPUT SIGNAL CIRCUIT MALFUNCTION
DTC P1615, DTC U1101COMMUNICATION ERROR FROM DISTANCE CONTROL ECU
TO ECM
DTC P1616, DTC U0100COMMUNICATION ERROR FROM ECM TO DISTANCE
CONTROL ECU
DTC P1617DISTANCE CONTROL ECU MALFUNCTION
DTC P1630, DTC U0122COMMUNICATION ERROR FROM VSC TO ECM
DTC P1631, DTC U0100COMMUNICATION ERROR FROM ECM TO VSC
DTC P1575WARNING BUZZER MALFUNCTION
DTC P1578BRAKE SYSTEM MALFUNCTION
DTC U0235LOST COMMUNICATION WITH CRUISE CONTROL FRONT
DISTANCE RANGE SENSOR

CIRCUIT DESCRIPTION
SEE CIRCUIT DESCRIPTION
.
Fig. 44: DTC P0500 And P0503 Problem Symptom Diagnostic Chart

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
WIRING DIAGRAM
SEE WIRING DIAGRAM
.
INSPECTION PROCEDURE
SEE INSPECTION PROCEDURE
.
CIRCUIT DESCRIPTION
When the brake pedal is depressed, the stop lamp switch assy sends a signal to the ECM. When the ECM
receives this signal, it cancels the cruise control.
The fail-safe function operates to enable normal driving even if there is a malfunction in the stop lamp signal
circuit.
The cancel condition occurs when positive battery voltage is applied to terminal STP.
When the brake is applied, battery positive voltage is normally applied to terminal STP of the ECM through the
STOP fuse and the stop lamp switch ass
y, and the ECM turns the cruise control off.

b. Turn the ignition switch to the ON position, and turn the hand-held tester main switch on.
c. Select the item "STP LIGHT SW M", "STP LIGHT SW S1" or "STP LIGHT SW S2" in the DATA
LIST, and read its value displayed on the hand-held tester.
d. Check that the stop lamp comes on when the brake pedal is depressed, and goes off when the brake
pedal is released.
CC (ECM):
DATA LIST (CC (ECM))
OK: When brake pedal operation is performed, the standard values will be above.
NG: Go to step 2
OK: REPLACE ECM (SEE REPLACEMENT
)
2.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:
STOP LAMP SWITCH TERMINALS RESISTANCE SPECIFICATION
NG: REPLACE STOP LAMP SWITCH ASSY
ItemMeasurement Item / Display
(Range)Normal ConditionDiagnostic
Note
STP LIGHT
SW MStop lamp SW signal (Main
CPU) / ON or OFFON: Brake pedal depressed OFF:
Brake pedal released-
STP LIGHT
SW S1Stop lamp SW signal (Sub CPU) /
ON or OFFON: Brake pedal depressed OFF:
Brake pedal released-
STP LIGHT
SW S2Stop lamp SW signal (Sub CPU) /
ON or OFFON: Brake pedal depressed OFF:
Brake pedal released-
Switch conditionTester connectionSpecified value
Switch pin free1 - 2Below 1 ohms
Switch pin free3 - 410 kohms or higher
Switch pin pushed in1 - 210 kohms or higher
Switch pin pushed in3 - 4Below 1 ohms

Fig. 48: Identifying Stop Lamp Switch Assy Connector
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR
OK: Go To Next Step.
4.INSPECT ECM
a. Reconnect the stop lamp switch connector.
b. Disconnect the E2 and E3 connectors from the ECM.
c. Turn the ignition switch to the ON position.
d. Measure the voltage according to the value(s) in the table below.
Standard:
ECM CONNECTOR TERMINALS VOLTAGE SPECIFICATION
Pedal conditionTester connectionSpecification
DepressedE2-4 (STP) - Body ground10 to 14V
ReleasedE2-4 (STP) - Body groundBelow 1 V

Result:
RESULT DETAIL
B: Go to step 5
C: REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LAMP SWITCH - ECM)
DepressedE3-8 (ST1-) - Body groundBelow 1 V
ReleasedE3-8 (ST1-) - Body ground10 to 14V
OKA
NG (STP terminal is NG)B
NG (ST1- terminals is NG)C

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
A: REPLACE ECM (SEE REPLACEMENT
)
5.INSPECT DRIVER SIDE J/B
a. Measure the voltage according to the value(s) in the table below.
Fig. 50: Identifying Driver Side Junction Block ECU Connector Terminals

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
Standard:
TESTER CONNECTION SPECIFICATION
NG: Go to step 6
Pedal conditionTester connectionSpecification
DepressedD3-12 (STPO) - Body ground10 to 14V
ReleasedD3-12 (STPO) - Body groundBelow 1 V

OK: REPAIR OR REPLACE HARNESS OR CONNECTOR (DRIVER SIDE J/B ECU - ECM)
6.INSPECT DRIVER SIDE J/B
a. Measure the voltage according to the value(s) in the table below.
Fig. 51: Identifying Driver Side Junction Block ECU Connector Terminals

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
Standard:
ECU CONNECTOR TERMINALS VOLTAGE SPECIFICATION
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR (STOP LAMP SWITCH - DRIVER
SIDE J/B ECU)
OK: REPLACE DRIVER SIDE J/B
Pedal conditionTester connectionSpecification
DepressedD3-13 (STPI) - Body ground10 to 14V
ReleasedD3-13 (STPI) - Body groundBelow 1 V

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.
Fig. 52: DTC P0607 Problem Symptom Diagnostic Chart

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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 millimeter wave
radar sensor and then sends a brake control demand signal (deceleration demand) and diagnosis signals, such as
millimeter wave radar sensor grime or millimeter wave radar sensor malfunction, to the ECM.