Toyota Tundra Service Manual: Headlight (HI-BEAM) Circuit

Toyota Tundra Service Manual / Vehicle Interior / Lighting / Lighting System / Headlight (HI-BEAM) Circuit

DESCRIPTION

The main body ECU (multiplex network body ECU) receives headlight dimmer switch information signals and illuminates the high beam headlights.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.	PERFORM ACTIVE TEST USING TECHSTREAM

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

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Main Body

Tester Display	Test Part	Control Range	Diagnostic Note
Head Light Hi	Headlight dimmer relay (DIMMER)	OFF or ON	-

OK:

Headlight dimmer relay (DIMMER) operates (high beam headlights turn on).

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

2.	INSPECT HEADLIGHT DIMMER RELAY (DIMMER)

(a) Remove the headlight dimmer relay (DIMMER) from the engine room relay block and junction block.

(b) Inspect the headlight dimmer relay (DIMMER).

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REPLACE HEADLIGHT DIMMER RELAY (DIMMER)

3.	CHECK HARNESS AND CONNECTOR (HEADLIGHT DIMMER RELAY [DIMMER] - BATTERY)

(a) Remove the headlight dimmer relay (DIMMER) from the engine room relay block and junction block.

*a	Front view of wire harness connector (to Headlight Dimmer Relay [DIMMER])

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
Headlight dimmer relay (DIMMER) terminal 3 - Body ground	Always	11 to 14 V
Headlight dimmer relay (DIMMER) terminal 1 - Body ground	Always	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	CHECK HARNESS AND CONNECTOR (HEADLIGHT DIMMER RELAY [DIMMER] - MAIN BODY ECU [MULTIPLEX NETWORK BODY ECU] AND HEADLIGHT ASSEMBLY)

(a) Remove the headlight dimmer relay (DIMMER) from the engine room relay block and junction block.

(b) Disconnect the J165 main body ECU (multiplex network body ECU) connector.

(1) Disconnect the A8 headlight assembly LH connector.

(2) Disconnect the A9 headlight assembly RH connector.

(d) for LED Headlight:

(1) Disconnect the A59 headlight assembly LH connector.

(2) Disconnect the A58 headlight assembly RH connector.

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

Standard Resistance:

for Halogen Headlight

Tester Connection	Condition	Specified Condition
Headlight dimmer relay (DIMMER) terminal 2 - J165-1 (DIM)	Always	Below 1 Ω
Headlight dimmer relay (DIMMER) terminal 5 - A8-2 (HI)	Always	Below 1 Ω
Headlight dimmer relay (DIMMER) terminal 2 or J165-1 (DIM) - Body ground	Always	10 kΩ or higher
Headlight dimmer relay (DIMMER) terminal 5 or A8-2 (HI) - Body ground	Always	10 kΩ or higher

for LED Headlight

Tester Connection	Condition	Specified Condition
Headlight dimmer relay (DIMMER) terminal 2 - J165-1 (DIM)	Always	Below 1 Ω
Headlight dimmer relay (DIMMER) terminal 5 - A59-1 (HI)	Always	Below 1 Ω
Headlight dimmer relay (DIMMER) terminal 2 or J165-1 (DIM) - Body ground	Always	10 kΩ or higher
Headlight dimmer relay (DIMMER) terminal 5 or A59-1 (HI) - Body ground	Always	10 kΩ or higher

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

REPAIR OR REPLACE HARNESS OR CONNECTOR

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Headlight Dimmer Switch Circuit

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Toyota Tundra Service Manual: Headlight (HI-BEAM) Circuit

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