LIGHTING SYSTEM > Headlight Signal Circuit

for Preparation Click here


DESCRIPTION

  1. This circuit is only for vehicles with the daytime running light system or with automatic light control system.

    HINT:
    1. For vehicles with the daytime running light system or with automatic light control system, the exterior lights (headlights, taillights, front fog lights and rear fog light) are controlled by the main body ECU.
    2. For vehicles without the daytime running light system and without automatic light control system, the exterior lights (headlights, taillights, front fog lights, and rear fog light) are not controlled by the main body ECU, so perform troubleshooting according to the Problem Symptoms Table (Click here).
    3. The main body receives the light control switch HEAD signal to control the headlight relay.

  2. When the light control switch is in the AUTO position, the main body ECU receives the ambient light level signal from the automatic light control sensor to control the headlight relay.

    HINT:
    1. If a low beam headlight bulb on only one side does not illuminate, inspect the bulb, fuse, or wire harness that is related to the bulb.
    2. If both right and left low beam headlights do not illuminate when the light control switch is turned to the HEAD position, perform the headlight relay Active Test and read the light control switch HEAD signal value in the Data List to determine if the malfunction exists on the switch side or the relay side.

  3. When both of the following conditions are met, the high beam headlights come on.
    - Low beam headlights are turned on by the automatic light control or manual light control.
    - Dimmer switch is in HIGH position.
  4. When the dimmer switch is turned to the HIGH FLASH position, the high beam headlights come on.

    HINT:
    1. If a high beam headlight on only one side does not illuminate, inspect the fuse, bulb, or wire harness that is related to the bulb.
    2. If both right and left high beam headlights do not illuminate when the low beam headlights are on and dimmer switch is turned to HIGH position, perform the high beam headlight relay Active Test, and read the dimmer switch HIGH signal value in the Data List to determine if the malfunction exists on either the switch side or the relay side.


WIRING DIAGRAM


E177353E01


INSPECTION PROCEDURE

NOTICE:
Inspect the fuses and bulbs for circuits related to this system before performing the following inspection procedure.

1.CHECK HEADLIGHT ILLUMINATION

  1. Check the illumination condition of the headlights.
    Result 
    Result
    		Proceed to
    LO-beam headlight does not illuminate
    		A
    HI-beam headlight does not illuminate
    		B



B
Go to step 11
A


2.PERFORM ACTIVE TEST USING INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the tester on.

  1. Enter the following menus: Body / Main Body / Active Test.

  1. According to the display on the tester, perform the Active Test.

    Main Body 
    Tester Display
    		Test Part
    		Control Range
    		Diagnostic Note
    Headlight Relay
    		Headlight Relay
    		ON or OFF
    		-

    OK:
    Headlight relay operates (Low beam headlights illuminate).



NG
Go to step 3
OK

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE (Click here)  

3.READ VALUE USING INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the tester on.

  1. Enter the following menus: Body / Main Body / Data List.

  1. According to the display on the tester, read the Data List.

    Main Body 
    Tester Display
    		Test Part
    		Control Range
    		Diagnostic Note
    Head Light SW (Head)
    		Light control switch HEAD signal
    ON or OFF
    		ON: Light control switch in HEAD
    OFF: Light control switch not in HEAD
    		-

    OK:
    Normal conditions listed above are displayed.



NG
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE (Click here)
OK


4.CHECK HARNESS AND CONNECTOR (HEADLIGHT ASSEMBLY - HEADLIGHT RELAY)


    E174474E01

  1. Disconnect the A7 or A14 headlight assembly connector.

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

    Standard Voltage:
    LH Side 
    Tester Connection
    		Switch Condition
    		Specified Condition
    A7-1 (B) - Body ground
    		Light control switch OFF → HEAD
    		Below 1 V → 11 to 14 V
    RH Side 
    Tester Connection
    		Switch Condition
    		Specified Condition
    A14-1 (B) - Body ground
    		Light control switch OFF → HEAD
    		Below 1 V → 11 to 14 V

    Text in Illustration 
    *1
    		Front view of wire harness connector
    (to Headlight Assembly)
    *2
    		LH Side
    *3
    		RH Side

  1. Reconnect the headlight assembly connector.



NG
Go to step 5
OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (HEADLIGHT ASSEMBLY - BODY GROUND) 

5.INSPECT HEADLIGHT RELAY (H-LP)


    E125026

  1. Remove the headlight relay from the No. 2 engine room relay block.

  1. 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
    Apply the battery voltage between terminals 1 and 2
    		Below 1 Ω

  1. Reinstall the headlight relay.



NG
REPLACE HEADLIGHT RELAY
OK


6.CHECK HARNESS AND CONNECTOR (BATTERY - HEADLIGHT RELAY)


    E174469E01

  1. Remove the headlight relay from the No. 2 engine room relay block.

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

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    Headlight relay terminal 1 - Body ground
    		Always
    		11 to 14 V
    Headlight relay terminal 5 - Body ground
    		Always
    		11 to 14 V

    Text in Illustration 
    *1
    		Component without relay connected
    (No. 2 Engine Room Relay Block)
    *2
    		Headlight Relay

  1. Reinstall the headlight relay.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


7.CHECK HARNESS AND CONNECTOR (HEADLIGHT RELAY - HEADLIGHT ASSEMBLY)


    E174473E01

  1. Remove the headlight relay from the No. 2 engine room relay block.

  1. Disconnect the A7 or A14 headlight assembly connector.

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

    Standard Resistance:
    LH Side 
    Tester Connection
    		Condition
    		Specified Condition
    Headlight relay terminal 3 - A7-1 (B)
    		Always
    		Below 1 Ω
    Headlight relay terminal 3 - Body ground
    		Always
    		10 kΩ or higher
    RH Side 
    Tester Connection
    		Condition
    		Specified Condition
    Headlight relay terminal 3 - A14-1 (B)
    		Always
    		Below 1 Ω
    Headlight relay terminal 3 - Body ground
    		Always
    		10 kΩ or higher

    Text in Illustration 
    *1
    		Component without relay connected
    (No. 2 Engine Room Relay Block)
    *2
    		Front view of wire harness connector
    (to Headlight Assembly)
    *3
    		Headlight Relay
    *4
    		LH Side
    *5
    		RH Side

  1. Reinstall the headlight relay.

  1. Reconnect the headlight assembly connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


8.CHECK HARNESS AND CONNECTOR (HEADLIGHT RELAY - INSTRUMENT PANEL JUNCTION BLOCK)


    E174471E01

  1. Remove the headlight relay from the No. 2 engine room relay block.

  1. Disconnect the 3B instrument panel junction block connector.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    Headlight relay terminal 2 - 3B-34
    		Always
    		Below 1 Ω
    3B-34 - Body ground
    		Always
    		10 kΩ or higher

Text in Illustration 
*1
Component without relay connected
(No. 2 Engine Room Relay Block)
*2
Front view of wire harness connector
(to Instrument Panel Junction Block)
*3
Headlight Relay

  1. Reinstall the headlight relay

  1. Reconnect the instrument panel junction block connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


9.REPLACE MAIN BODY ECU

  1. Temporarily replace the main body ECU with a new or normally functioning one (Click here).


NEXT


10.PERFORM ACTIVE TEST USING INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the tester on.

  1. Enter the following menus: Body / Main Body / Active Test.

  1. According to the display on the tester, perform the Active Test.

    Main Body 
    Tester Display
    		Test Part
    		Control Range
    		Diagnostic Note
    Headlight Relay
    		Headlight Relay
    		ON or OFF
    		-

    OK:
    Headlight relay operates (Low beam headlights illuminate).



NG
REPLACE INSTRUMENT PANEL JUNCTION BLOCK
OK

END (MAIN BODY ECU DEFECTIVE) 

11.PERFORM ACTIVE TEST USING INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the tester on.

  1. Enter the following menus: Body / Main Body / Active Test.

  1. According to the display on the tester, perform the Active Test.

    Main Body 
    Tester Display
    		Test Part
    		Control Range
    		Diagnostic Note
    Head Light (HI)
    		Headlight dimmer relay
    		ON or OFF
    		-

    OK:
    Headlight dimmer relay operates (High beam headlights illuminate).



NG
Go to step 12
OK

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE (Click here)  

12.READ VALUE USING INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the tester on.

  1. Enter the following menus: Body / Main Body / Data List.

  1. According to the display on the tester, read the Data List.

    Main Body 
    Tester Display
    		Test Part
    		Control Range
    		Diagnostic Note
    Dimmer SW
    		Dimmer switch HIGH signal
    ON or OFF
    		ON: Dimmer switch in HIGH or HIGH FLASH
    OFF: Dimmer switch in LOW
    		-
    Passing Light SW
    		Dimmer switch HIGH FLASH signal
    ON or OFF
    		ON: Dimmer switch in HIGH FLASH (PASS)
    OFF: Dimmer switch not in HIGH FLASH (PASS)
    		-

    OK:
    Normal conditions listed above are displayed.



NG
PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE (Click here)
OK


13.CHECK HARNESS AND CONNECTOR (HEADLIGHT ASSEMBLY - HEADLIGHT DIMMER RELAY)


    E174474E03

  1. Disconnect the A7 or A14 headlight assembly connector.

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

    Standard Voltage:
    LH Side 
    Tester Connection
    		Switch Condition
    		Specified Condition
    A7-3 (B) - Body ground
    		Light control switch OFF → HEAD
    		Below 1 V → 11 to 14 V
    RH Side 
    Tester Connection
    		Switch Condition
    		Specified Condition
    A14-3 (B) - Body ground
    		Light control switch OFF → HEAD
    		Below 1 V → 11 to 14 V

    Text in Illustration 
    *1
    		Front view of wire harness connector
    (to Headlight Assembly)
    *2
    		LH Side
    *3
    		RH Side

  1. Reconnect the headlight assembly connector.



NG
Go to step 14
OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (HEADLIGHT ASSEMBLY - BODY GROUND) 

14.INSPECT HEADLIGHT DIMMER RELAY (DIM)


    B016200

  1. Remove the headlight dimmer relay from the No. 2 engine room relay block.

  1. 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
    Apply the battery voltage between terminals 1 and 2
    		Below 1 Ω

  1. Reinstall the headlight dimmer relay.



NG
REPLACE HEADLIGHT DIMMER RELAY
OK


15.CHECK HARNESS AND CONNECTOR (BATTERY - HEADLIGHT DIMMER RELAY)


    E174470E01

  1. Remove the headlight dimmer relay from the No. 2 engine room relay block.

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

    Standard Voltage:
    Tester Connection
    		Switch Condition
    		Specified Condition
    Headlight relay terminal 1 - Body ground
    		Light control switch OFF → HEAD
    		Below 1 V → 11 to 14 V
    Headlight relay terminal 5 - Body ground
    		Light control switch OFF → HEAD
    		Below 1 V → 11 to 14 V

    Text in Illustration 
    *1
    		Component without relay connected
    (No. 2 Engine Room Relay Block)
    *2
    		Headlight Dimmer Relay

  1. Reinstall the headlight dimmer relay.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


16.CHECK HARNESS AND CONNECTOR (HEADLIGHT ASSEMBLY - HEADLIGHT DIMMER RELAY)


    E174476E01

  1. Remove the headlight dimmer relay from the No. 2 engine room relay block.

  1. Disconnect the A7 or A14 headlight assembly connector.

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

    Standard Resistance:
    LH Side 
    Tester Connection
    		Condition
    		Specified Condition
    Headlight dimmer relay terminal 3 - A7-3 (B)
    		Always
    		Below 1 Ω
    Headlight dimmer relay terminal 3 - Body ground
    		Always
    		10 kΩ or higher
    RH Side 
    Tester Connection
    		Condition
    		Specified Condition
    Headlight dimmer relay terminal 3 - A14-3 (B)
    		Always
    		Below 1 Ω
    Headlight dimmer relay terminal 3 - Body ground
    		Always
    		10 kΩ or higher

    Text in Illustration 
    *1
    		Component without relay connected
    (No. 2 Engine Room Relay Block)
    *2
    		Front view of wire harness connector
    (to Headlight Assembly)
    *3
    		Headlight Dimmer Relay
    *4
    		LH Side
    *5
    		RH Side

  1. Reinstall the headlight dimmer relay.

  1. Reconnect the headlight assembly connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


17.CHECK HARNESS AND CONNECTOR (HEADLIGHT DIMMER RELAY - INSTRUMENT PANEL JUNCTION BLOCK)


    E174475E01

  1. Remove the headlight dimmer relay from the No. 2 engine room relay block.

  1. Disconnect the 3B instrument panel junction block connector.

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

    Standard Resistance:
    Tester Connection
    		Condition
    		Specified Condition
    Headlight dimmer relay terminal 2 - 3B-25
    		Always
    		Below 1 Ω
    3B-25 - Body ground
    		Always
    		10 kΩ or higher

Text in Illustration 
*1
Component without relay connected
(No. 2 Engine Room Relay Block)
*2
Front view of wire harness connector
(to Instrument Panel Junction Block)
*3
Headlight Dimmer Relay

  1. Reinstall the headlight dimmer relay

  1. Reconnect the instrument panel junction block connector.



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


18.REPLACE MAIN BODY ECU

  1. Temporarily replace the main body ECU with a new or normally functioning one (Click here).


NEXT


19.PERFORM ACTIVE TEST USING INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the tester on.

  1. Enter the following menus: Body / Main Body / Active Test.

  1. According to the display on the tester, perform the Active Test.

    Main Body 
    Tester Display
    		Test Part
    		Control Range
    		Diagnostic Note
    Head Light (HI)
    		Headlight dimmer relay
    		ON or OFF
    		-

    OK:
    Headlight dimmer relay operates (High beam headlights illuminate).



NG
REPLACE INSTRUMENT PANEL JUNCTION BLOCK
OK

END (MAIN BODY ECU DEFECTIVE)