Lexus NX: High Beam Headlight Circuit

Lexus NX Service Manual / Vehicle Exterior / Lighting (ext) / Lighting System (for Single Beam Headlight) / 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.
Recognition code registration is necessary when replacing the main body ECU (multiplex network body ECU).
If the main body ECU (multiplex network body ECU) is replaced, refer to Registration.

PROCEDURE

1.	PERFORM ACTIVE TEST USING TECHSTREAM (HEADLIGHT HI)

(a) Using the Techstream, perform the Active Test.

Click here

Body Electrical > Main Body > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
Head Light Hi	Headlight dimmer relay	ON or OFF	-

Body Electrical > Main Body > Active Test

Tester Display
Head Light Hi

OK:

Headlight relay operates. (Hi beam headlights illuminate with the appropriate brightness.)

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

2.	CHECK HEADLIGHT DIMMER RELAY (H-LP LH/DIMMER [HI])

(a) Remove the headlight dimmer relay (H-LP LH/DIMMER [HI]) from the engine room relay block.

(b) Inspect the headlight dimmer relay (H-LP LH/DIMMER [HI]).

REPLACE HEADLIGHT DIMMER RELAY (H-LP LH/DIMMER [HI])

3.	CHECK HARNESS AND CONNECTOR (H-LP LH/DIMMER [HI] - BATTERY)

(a) Remove the headlight dimmer relay (H-LP LH/DIMMER [HI]) from the engine room relay block.

*a	Front view of wire harness connector (to Headlight Dimmer Relay [H-LP LH/DIMMER (HI)])

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
Relay terminal 5 - Body ground	Power switch off	11 to 14 V
Relay terminal 1 - Body ground	Always	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	CHECK HARNESS AND CONNECTOR (H-LP LH/DIMMER [HI] - HEADLIGHT ASSEMBLY)

*1: for LH
*2: for RH

(a) Remove the headlight dimmer relay (H-LP LH/DIMMER [HI]) from the engine room relay block.

(b) Disconnect the A66*1 and A68*2 headlight assembly connector.

Standard Resistance:

for LH

Tester Connection	Condition	Specified Condition
Relay terminal 3 - A66-1 (HI)	Always	Below 1 Ω
Headlight relay terminal 3 - Body ground	Always	10 kΩ or higher

for RH

Tester Connection	Condition	Specified Condition
Relay terminal 3 - A68-1 (HI)	Always	Below 1 Ω
Headlight relay terminal 3 - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

5.	CHECK HARNESS AND CONNECTOR (H-LP LH/DIMMER [HI] - MAIN BODY ECU [MULTIPLEX NETWORK BODY ECU])

(a) Remove the headlight dimmer relay (H-LP LH/DIMMER [HI]) from the engine room relay block.

(b) Disconnect the I46 main body ECU (multiplex network body ECU) connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
Relay terminal 2 - I46-1 (DIM)	Always	Below 1 Ω
Relay terminal 2 or I46-1 (DIM) - Body ground	Always	10 kΩ or higher

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

REPAIR OR REPLACE HARNESS OR CONNECTOR

SEE MORE:

Problem Symptoms Table

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Lexus NX: High Beam Headlight Circuit

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