Toyota Tacoma 2015-2018 Service Manual: Low Beam Headlight Circuit

Toyota Tacoma 2015-2018 Service Manual / Lighting / Lighting System / Low Beam Headlight Circuit

DESCRIPTION

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

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following inspection procedure.
If the main body ECU (multiplex network body ECU) is replaced, refer to Registration (See page ).*1
- *1: w/ Smart Key System

PROCEDURE

1.	PERFORM ACTIVE TEST USING TECHSTREAM (HEADLIGHT RELAY)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

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

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

Main Body

Tester Display	Test Part	Control Range	Diagnostic Note
Headlight Relay	Headlight relays	ON/OFF	-

OK:

Headlight relays operate. (Low beam headlights illuminate.)

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

2.	INSPECT H-LP LO RELAY

(a) Remove the H-LP LO relay from the engine room relay block.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
3 - 5	Voltage is not applied between terminals 1 and 2	10 kΩ or higher
3 - 5	Voltage is applied between terminals 1 and 2	Below 1 Ω

REPLACE H-LP LO RELAY

3.	CHECK HARNESS AND CONNECTOR (BATTERY - H-LP LO RELAY)

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
Relay terminal 2 - Body ground	Always	11 to 14 V
Relay terminal 5 - Body ground	Always	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	CHECK HARNESS AND CONNECTOR (H-LP LO RELAY - DRIVER SIDE JUNCTION BLOCK)

(a) Disconnect the 1F driver side junction block connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
Relay terminal 1 - 1F-28	Always	Below 1 Ω
1F-28 - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

5.	INSPECT DRIVER SIDE JUNCTION BLOCK

(a) Remove the driver side junction block.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
1F-28 - MB-15 (HRLY)	Always	Below 1 Ω
1F-28 - Body ground	Always	10 kΩ or higher

Text in Illustration

*a	Component without harness connected (Driver Side Junction Block)

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

REPLACE DRIVER SIDE JUNCTION BLOCK

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