Toyota Tacoma (2015-2018) Service Manual: Headlight Dimmer Switch Circuit

Toyota Tacoma (2015-2018) Service Manual / Lighting / Lighting System / Headlight Dimmer Switch Circuit

DESCRIPTION

The main body ECU (multiplex network body ECU) receives the following switch information:

Light control switch position is off (DRL OFF), tail, head or AUTO (DRL).
Dimmer switch position is high, low or high flash (pass).
Front fog light switch position is on or off.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

If the main body ECU (multiplex network body ECU) is replaced, refer to Registration (See page ).*1

*1: w/ Smart Key System

PROCEDURE

1.	READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(d) Enter the following menus: Body Electrical / Main Body / Data List.

(e) According to the display on the Techstream, read the Data List.

Main Body

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
Dimmer SW	Dimmer switch high position signal/ON or OFF	ON: Dimmer switch in high or high flash (pass) position OFF: Dimmer switch in low position	-
Passing Light SW	Dimmer switch high flash (pass) position signal/ON or OFF	ON: Dimmer switch in high flash (pass) position OFF: Dimmer switch not in high flash (pass) position	-
Front Fog Light SW	Front fog light switch signal/ON or OFF	ON: Front fog light switch ON OFF: Front fog light switch off	w/ Fog Light
Auto Light SW	Light control switch AUTO position signal/ON or OFF	ON: Light control switch in AUTO position OFF: Light control switch not in AUTO position	w/ Automatic High Beam System
Head Light SW	Light control switch head position signal/ON or OFF	ON: Light control switch in head position OFF: Light control switch not in head position	-
Tail Light SW	Light control switch tail position signal/ON or OFF	ON: Light control switch in tail or head position OFF: Light control switch in neither tail nor head position	-

OK:

Normal conditions listed above are displayed.

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

2.	INSPECT HEADLIGHT DIMMER SWITCH ASSEMBLY

HINT:

Inspect the items that did not change as a result of monitoring the Data List.

(a) Remove the headlight dimmer switch assembly (See page ).

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

Standard Resistance:

Light Control Switch

Tester Connection	Switch Condition	Specified Condition
18 (T) - 15 (EL)	Light control switch off	10 kΩ or higher
19 (H) - 15 (EL)		10 kΩ or higher
20 (A) - 15 (EL)		10 kΩ or higher
18 (T) - 15 (EL)	Light control switch in tail position	Below 1 Ω
18 (T) - 15 (EL)	Light control switch in head position	Below 1 Ω
19 (H) - 15 (EL)	Light control switch in head position	Below 1 Ω
20 (A) - 15 (EL)*1	Light control switch in AUTO position	Below 1 Ω

Dimmer Switch

Tester Connection	Switch Condition	Specified Condition
14 (HU) - 15 (EL)	Dimmer switch in low position	10 kΩ or higher
14 (HU) - 15 (EL)	Dimmer switch in high position	Below 1 Ω
17 (HF) - 15 (EL)	Dimmer switch in high flash position	Below 1 Ω

Fog Light Switch (w/ Fog Light)

Tester Connection	Switch Condition	Specified Condition
9 (BFG) - 8 (LFG)	Fog light switch off	10 kΩ or higher
9 (BFG) - 8 (LFG)	Fog light switch ON	Below 1 Ω

*1: w/ Automatic High Beam System

OK:

Headlight dimmer switch assembly is normal

Text in Illustration

*a	Component without harness connected (Headlight Dimmer Switch Assembly)

REPLACE HEADLIGHT DIMMER SWITCH

3.	CHECK HARNESS AND CONNECTOR (MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) - HEADLIGHT DIMMER SWITCH ASSEMBLY

(a) Disconnect the C11 headlight dimmer switch assembly connector.

(b) Disconnect the M6 main body ECU (multiplex network body ECU) connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
C11-9 (BFG) - M6-26 (FFOG)	Always	Below 1 Ω
C11-14 (HU) - M6-24 (HU)	Always	Below 1 Ω
C11-17 (HF) - M6-10 (HF)	Always	Below 1 Ω
C11-18 (T) - M6-22 (TAIL)	Always	Below 1 Ω
C11-19 (H) - M6-12 (HEAD)	Always	Below 1 Ω
C11-20 (A) - M6-8 (A)	Always	Below 1 Ω
C11-9 (BFG) - Body ground	Always	10 kΩ or higher
C11-14 (HU) - Body ground	Always	10 kΩ or higher
C11-17 (HF) - Body ground	Always	10 kΩ or higher
C11-18 (T) - Body ground	Always	10 kΩ or higher
C11-19 (H) - Body ground	Always	10 kΩ or higher
C11-20 (A) - Body ground	Always	10 kΩ or higher
C11-15 (EL) - Body ground	Always	Below 1 Ω
C11-8 (LFG) - Body ground	Always	Below 1 Ω

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

REPAIR OR REPLACE HARNESS OR CONNECTOR

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