Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: High Beam Headlight Circuit

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Exterior / Lighting (ext) / Lighting System (w/o Automatic Headlight Beam Level Control System) / High Beam Headlight Circuit

DESCRIPTION

The main body ECU (multiplex network body ECU) controls the high beam headlights.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • Before replacing the main body ECU (multiplex network body ECU), refer to Registration.

    Click here

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Main Body / Active Test.

(e) Perform the Active Test according to the display on the Techstream.

Body Electrical > Main Body > Active Test

Tester Display

Measurement Item

Control Range

Diagnostic Note

Head Light Hi

High beam headlights

OFF/ON

-
Body Electrical > Main Body > Active Test

Tester Display

Head Light Hi

OK:

High beam headlights illuminate.

OK

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

NG

2.

CHECK SEMICONDUCTOR POWER INTEGRATION ECU

(a) Using a voltmeter, check the signal reading of the semiconductor power integration ECU.

Click here

OK:

Output signal reading is normal.

NG

INSPECT SEMICONDUCTOR POWER INTEGRATION ECU (RESULTS OF SIGNAL READING CHECK)

OK

3.

CHECK HARNESS AND CONNECTOR (SEMICONDUCTOR POWER INTEGRATION ECU POWER SOURCE AND BODY GROUND)

*a

Component without semiconductor power integration ECU connected

(Engine Room Relay Block and Junction Block Assembly)

-

-

(a) Remove the semiconductor power integration ECU from the engine room relay block and junction block assembly.

Click here

(b) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Condition

Specified Condition

B-1 (BATT) - Body ground

Always

11 to 14 V

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

1D-14 (GND1) - Body ground

Always

Below 1 Ω

1G-5 (GND2) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

4.

CHECK HARNESS AND CONNECTOR (SEMICONDUCTOR POWER INTEGRATION ECU - MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU))

(a) Disconnect the J8 main body ECU (multiplex network body ECU) connector.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

1D-2 (-S) - J8-1 (DIM)

Always

Below 1 Ω

1D-2 (-S) or J8 -1 (DIM) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

5.

REPLACE SEMICONDUCTOR POWER INTEGRATION ECU

(a) Replace the semiconductor power integration ECU with a new one.

Click here

NEXT

6.

CHECK OPERATION (HIGH BEAM HEADLIGHTS)

(a) Check the operation of the high beam headlights.

OK:

High beam headlights operate normally.

OK

END (SEMICONDUCTOR POWER INTEGRATION ECU WAS DEFECTIVE)
NG

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

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