2003 LEXUS LS430 fuse diagram

Fig. 51: Rear Door RH ECU Power Source Circuit -Wiring Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
1.INSPECT FUSE (MPX-IG, AM1, RR DOOR RH, MPX-B1, D/C CUT)
a. Remove the MPX-IG and AM1 fuses from the driver side J/B.
b. Remove the MPX-B1 and RR DOOR RH fuses from the passenger side J/B.
c. Remove the D/C CUT fuse from the FL block assy.
d. Measure the resistance.
Standard: Below 1 ohms
NG: REPLACE FUSE
OK: Go to Next Step.
2.INSPECT RELAY (Marking: D-IG1)
a. Remove the D-IG1 relay from the driver side J/B.
b. Measure the resistance.
Fig. 52: Inspecting Relay (D
-IG1)
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

CIRCUIT DESCRIPTION
See CIRCUIT DESCRIPTION
.
Fig. 42: 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.

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.

Fig. 45: ECU Power Source Circuit - Wiring Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
1.INSPECT FUSE (MPX-B1, AM2, D/C CUT)
a. Remove the MPX-B1 and AM2 fuses from the passenger side J/B.
b. Remove the D/C CUT fuse from the FL block.
c. Measure the resistance of the fuse.
Standard: Below 1ohms
NG: REPLACE FUSE
OK: Go to next step

Fig. 18: Power Source Circuit (Driver Door ECU) - Wiring Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
1.INSPECT FUSE (MPX-B1, AM1, MPX-IG, D DOOR)
a. Remove the MPX-IG and AM1 fuses from the driver side J/B.
b. Remove the D DOOR and MPX-B1 fuses from the passenger side J/B.
c. Measure the resistance of the fuse.
Standard: Below 1 ohms

SYSTEM DIAGRAM
Fig. 2: Identifying Horn System Diagram

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
PROBLEM SYMPTOMS TABLE
Fig. 3: Problem Symptoms Table

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION
1.INSPECT FUSE (HORN)

Fig. 14: Wiring Diagram - Driver Door ECU Power Source Circuit
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
INSPECTION PROCEDURE
1.INSPECT FUSE (MPX-IG, AM1, D DOOR, MPX-B1, D/C CUT)
a. Remove the MPX-IG and AM1 fuses from the driver side J/B.
b. Remove the D DOOR and MPX-B1 fuses from the passenger side J/B.
c. Remove the D/C CUT fuse from the FL block assy.
d. Measure the resistance.