LIGHTING SYSTEM Taillight Relay Circuit

DESCRIPTION

The main body ECU receives the light control switch tail signal to control the taillight 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 taillight relay.

Tech Tips


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

  • If the vehicle has automatic light control or daytime running light control, the exterior lights (headlights, taillights, front fog lights* and rear fog light) are controlled by the main body ECU.

  • If the vehicle does not have automatic light control or daytime running light control, the exterior lights (headlights, taillights, front fog lights* and rear fog light) are not controlled by the main body ECU. Perform troubleshooting according to the Problem Symptoms Table Click here.

  • When any of the lights do not illuminate, check the bulb or wire harness that is related to the light.

  • When none of the lights that are related to the tail relay illuminate and the TAIL fuse is normal, perform the taillight relay Active Test and read the light control switch tail signal value in the Data List to determine if the malfunction exists on either the switch side or the relay side.

  • The taillight relay is installed in the instrument panel junction block and cannot be removed for inspection.


WIRING DIAGRAM

A01IO0OE01

INSPECTION PROCEDURE

Note

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

PROCEDURE


  1. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (TAILLIGHT RELAY)


    1. Using the intelligent tester, perform the Active Test Click here.

      Main Body
      Tester Display Test Part Control Range Diagnostic Note
      Taillight Relay Taillight relay ON/OFF -
      OK
      Taillight relay operates (taillights illuminate).

    NG

    READ VALUE USING INTELLIGENT TESTER (HEADLIGHT DIMMER SWITCH) Click here

    OK

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

  2. READ VALUE USING INTELLIGENT TESTER (HEADLIGHT DIMMER SWITCH)


    1. Using the intelligent tester, read the Data List Click here.

      Main Body
      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Head Light SW (Tail) Light control switch tail signal / ON or OFF

      ON: Light control switch in tail or head

      OFF: Light control switch not in tail or head

      		 -
      OK
      The display is as specified in the normal condition column.

    NG

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

    OK

  3. CHECK HARNESS AND CONNECTOR (BATTERY - TAIL FUSE TERMINAL)

    A01IQHQE02
    Text in Illustration
    *1 Main Body ECU (Instrument Panel Junction Block)
    *2 TAIL Fuse

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      TAIL fuse terminal - Body ground Light control switch off Below 1 V
      Light control switch tail 11 to 14 V

    NG

    CHECK HARNESS AND CONNECTOR (BATTERY - MAIN BODY ECU) Click here

    OK

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  4. CHECK HARNESS AND CONNECTOR (BATTERY - MAIN BODY ECU)

    A01IPQRE15
    Text in Illustration
    *1

    Front view of wire harness connector

    (to Main Body ECU)

    1. Disconnect the DG main body ECU connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      DG-1 - Body ground Always 11 to 14 V

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE MAIN BODY ECU (INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)