LIGHTING SYSTEM Headlight Signal Circuit

DESCRIPTION

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

  Tech Tips

  
  

  • 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.

  • 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.

  • The main body receives the light control switch HEAD signal to control the headlight relay.

• 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.

  Tech Tips

  
  

  • 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.

  • 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.

• 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.

• When the dimmer switch is turned to the HIGH FLASH position, the high beam headlights come on.

  Tech Tips

  
  

  • 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.

  • 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

INSPECTION PROCEDURE

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

   PERFORM ACTIVE TEST USING INTELLIGENT TESTER Click here

   A

2. PERFORM ACTIVE TEST USING INTELLIGENT TESTER

   
   

   1. Connect the intelligent tester to the DLC3.

   2. Turn the ignition switch to ON.

   3. Turn the tester on.

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

   5. 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

   READ VALUE USING INTELLIGENT TESTER Click here

   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.

   2. Turn the ignition switch to ON.

   3. Turn the tester on.

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

   5. 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)

   
   
   1. 

      Text in Illustration

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

      Disconnect the A7 or A14 headlight assembly connector.

   2. 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

   3. Reconnect the headlight assembly connector.

   
   

   NG

   INSPECT HEADLIGHT RELAY (H-LP) Click here

   OK

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

5. INSPECT HEADLIGHT RELAY (H-LP)

   
   

   1. 

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

   2. 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

   3. Reinstall the headlight relay.

   
   

   NG

   REPLACE HEADLIGHT RELAY

   OK

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

   
   
   1. 

      Text in Illustration

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

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

   2. 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

   3. Reinstall the headlight relay.

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

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

   
   
   1. 

      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

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

   2. Disconnect the A7 or A14 headlight assembly connector.

   3. 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

   4. Reinstall the headlight relay.

   5. Reconnect the headlight assembly connector.

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

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

   
   
   1. 

      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

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

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

   3. 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

   4. Reinstall the headlight relay

   5. 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.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

    5. 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.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

    5. 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

    READ VALUE USING INTELLIGENT TESTER Click here

    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.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

    5. 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)

    
    
    1. 

       Text in Illustration

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

       Disconnect the A7 or A14 headlight assembly connector.

    2. 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

    3. Reconnect the headlight assembly connector.

    
    

    NG

    INSPECT HEADLIGHT DIMMER RELAY (DIM) Click here

    OK

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

14. INSPECT HEADLIGHT DIMMER RELAY (DIM)

    
    

    1. 

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

    2. 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

    3. Reinstall the headlight dimmer relay.

    
    

    NG

    REPLACE HEADLIGHT DIMMER RELAY

    OK

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

    
    
    1. 

       Text in Illustration

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

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

    2. 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

    3. Reinstall the headlight dimmer relay.

    
    

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

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

    
    
    1. 

       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

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

    2. Disconnect the A7 or A14 headlight assembly connector.

    3. 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

    4. Reinstall the headlight dimmer relay.

    5. 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)

    
    
    1. 

       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

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

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

    3. 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

    4. Reinstall the headlight dimmer relay

    5. 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.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

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

    5. 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)