Lexus IS250 · Service Manual BODY ELECTRICAL

Taillight Circuit

Circuit diagnosis

DESCRIPTION

Front light:
The front controller controls the operation of the FR TAIL relay. The FR TAIL relay turns on the front parking lights.
The front controller receives front parking light ON request signals from the combination switch ECU through BEAN communication and activates the FR TAIL relay.
The FR TAIL relay is built into the front controller, so unlike conventional relays, it cannot be removed for inspection.
Rear light:
The main body ECU RH controls the operation of the TAIL relay. The TAIL relay turns on the taillights and license plate lights.
The main body ECU RH receives taillight and license plate light ON request signals from the combination switch ECU through BEAN communication and activates the TAIL relay.
The TAIL relay is built into the cowl side J/B LH, so unlike conventional relays, it cannot be removed for inspection.

WIRING DIAGRAM

E123478E02
E123479E02

INSPECTION PROCEDURE

NOTICE:
Before proceeding to the following flowchart, check that the fuses are not blown and that the bulbs are not burned out.


1. CHECK TAILLIGHT (OPERATION)

  1. Turn the engine switch on (IG).

  1. When the taillight switch is operated, check that the following lights illuminate.

    HINT:
    1. The front lights (parking lights) share the same drive circuit. Therefore, if one of the front lights does not come on, there may be a problem in the circuit between the FR TAIL relay and bulb, or the circuit between the bulb and body ground. Inspect those circuits to identify the problem.
    2. The rear lights (taillights and license plate lights) share the same drive circuit. Therefore, if one of the rear lights does not come on, there may be a problem in the circuit between the TAIL relay and the bulb or LED, or the circuit between the bulb or LED and body ground. Inspect those circuits to identify the problem.


    Result:
    Result
    		 Proceed to
    Neither front nor rear lights illuminate
    		 A
    Front lights (parking lights) do not illuminate
    		 B
    Rear lights (taillights and license plate lights) do not illuminate
    		 C



B
Go to step 2

C
Go to step 6
A

PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE

2. PERFORM ACTIVE TEST BY INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG).

  1. Turn the intelligent tester on.

  1. Select the item(s) in the ACTIVE TEST, and check the operation.

    ACTIVE TEST: Body No. 5 (Front Controller) 
    Item
    		 Test Details
    		 Diagnostic Note
    Clearance Light Operation
    		 Clearance light (Front parking lights) ON / OFF
    		 -

    OK:
    Front parking lights illuminate.



 NG
Go to step 3
OK

REPLACE ENGINE ROOM NO. 2 R/B (FRONT CONTROLLER)

3. CHECK HARNESS AND CONNECTOR (HEADLIGHT - BODY GROUND)

HINT:
Perform the following inspection on either the LH or RH side.

  1. E108361E13
    Disconnect the B2 or B12 headlight connector.

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

    Standard resistance:
    RH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    B2-8 (E) - Body ground
    		 Always
    		 Below 1 Ω
    LH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    B12-8 (E) - Body ground
    		 Always
    		 Below 1 Ω



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


4. CHECK HARNESS AND CONNECTOR (HEADLIGHT - BODY GROUND)

HINT:
Perform the following inspection on either the LH or RH side.

  1. E108361E14
    Disconnect the B2 or B12 headlight connector.

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

    Standard voltage:
    RH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    B2-7 (B) - Body ground
    		 Engine switch off
    		 Below 1 V
    B2-7 (B) - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V
    LH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    B12-7 (B) - Body ground
    		 Engine switch off
    		 Below 1 V
    B12-7 (B) - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V



NG
Go to step 5
OK

REPLACE HEADLIGHT ASSEMBLY

5. CHECK HARNESS AND CONNECTOR (HEADLIGHT - ENGINE ROOM NO. 2 R/B)

HINT:
Perform the following inspection on either the LH or RH side.

  1. E123259E04
    Disconnect the B2 or B12 headlight connector.

  1. Disconnect the 2G engine room R/B No. 2 connector.

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

    Standard resistance:
    RH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    B2-7 (B) - 2G-8
    		 Always
    		 Below 1 Ω
    B2-7 (B) - Body ground
    		 Always
    		 10 kΩ or higher
    LH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    B12-7 (B) - 2G-9
    		 Always
    		 Below 1 Ω
    B12-7 (B) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE ENGINE ROOM NO. 2 R/B (FRONT CONTROLLER)

6. PERFORM ACTIVE TEST BY INTELLIGENT TESTER

  1. Connect the intelligent tester to the DLC3.

  1. Turn the engine switch on (IG).

  1. Turn the intelligent tester on.

  1. Select the item(s) in the ACTIVE TEST, and check the operation.

    ACTIVE TEST: Main Body (Main Body ECU RH) 
    Item
    		 Test Details
    		 Diagnostic Note
    Tail Light
    		 Taillights (taillights, license plate lights and side marker lights) ON / OFF
    		 -

    OK:
    Taillights and license plate lights illuminate.


    Result:
    Result
    		 Proceed to
    Inner taillights do not illuminate
    		 A
    Outer taillights do not illuminate
    		 B
    License plate lights do not illuminate
    		 C
    All rear lights illuminate
    		D
    All rear lights do not illuminate
    		E



B
Go to step 9

C
Go to step 11

D
REPLACE MAIN BODY ECU RH (COWL SIDE J/B RH)

E
Go to step 15
A


7. CHECK HARNESS AND CONNECTOR (INNER TAILLIGHT - BODY GROUND)

HINT:
Perform the following inspection on either the LH or RH side.

  1. E075377E02
    Disconnect the Q46 or Q40 inner taillight connector.

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

    Standard resistance:
    RH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q46-3 - Body ground
    		 Always
    		 Below 1 Ω
    LH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q40-3 - Body ground
    		 Always
    		 Below 1 Ω



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


8. CHECK HARNESS AND CONNECTOR (INNER TAILLIGHT - MAIN BODY ECU LH)

HINT:
Perform the following inspection on either the LH or RH side.

  1. E075377E02
    Disconnect the Q46 or Q40 inner taillight connector.

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

    Standard voltage:
    RH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q46-1 - Body ground
    		 Engine switch off
    		 Below 1 V
    Q46-1 - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V
    LH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q40-1 - Body ground
    		 Engine switch off
    		 Below 1 V
    Q40-1 - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE INNER COMBINATION LIGHT

9. CHECK HARNESS AND CONNECTOR (OUTER TAILLIGHT - BODY GROUND)

HINT:
Perform the following inspection on either the LH or RH side.

  1. E104066E04
    Disconnect the Q51 or Q50 outer taillight connector.

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

    Standard resistance:
    RH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q51-6 (E) - Body ground
    		 Always
    		 Below 1 Ω
    LH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q50-6 (E) - Body ground
    		 Always
    		 Below 1 Ω



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


10. CHECK HARNESS AND CONNECTOR (OUTER TAILLIGHT - MAIN BODY ECU LH)

HINT:
Perform the following inspection on either the LH or RH side.

  1. E104066E05
    Disconnect the Q51 or Q50 outer taillight connector.

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

    Standard voltage:
    RH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q51-3 (TL) - Body ground
    		 Engine switch off
    		 Below 1 V
    Q51-3 (TL) - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V
    LH side:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q50-3 (TL) - Body ground
    		 Engine switch off
    		 Below 1 V
    Q50-3 (TL) - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE OUTER COMBINATION LIGHT

11. CHECK HARNESS AND CONNECTOR (LICENSE PLATE LIGHT LH - BODY GROUND)

HINT:
Perform the following inspection on the LH side.

  1. E073289E02
    Disconnect the Q47 license plate light LH connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q47-2 (E)- Body ground
    		 Always
    		 Below 1 Ω



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


12. CHECK HARNESS AND CONNECTOR (LICENSE PLATE LIGHT RH - MAIN BODY ECU LH)

HINT:
Perform the following inspection on the RH side.

  1. E073289E03
    Disconnect the Q44 license plate light RH connector.

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q44-1 (B) - Body ground
    		 Engine switch off
    		 Below 1 V
    Q44-1 (B) - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


13. CHECK HARNESS AND CONNECTOR (LICENSE PLATE LIGHT RH - LICENSE PLATE LIGHT RH)

HINT:
Perform the following inspection on the LH side.

  1. E073289E04
    Connect the Q44 license plate light RH connector.

  1. Disconnect the Q47 license plate light LH connector.

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

    Standard Voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q47-1 (B) - Body ground
    		 Engine switch off
    		 Below 1 V
    Q47-1 (B) - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V



NG
Go to step 14
OK

REPLACE LICENSE PLATE LIGHT (LH SIDE)

14. CHECK HARNESS AND CONNECTOR (LICENSE PLATE LIGHT LH - LICENSE PLATE LIGHT RH)

  1. E073289E05
    Disconnect the Q44 license plate light RH connector.

  1. Disconnect the Q47 license plate light LH connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    Q44-2 (E) - Q47-1 (B)
    		 Always
    		 Below 1 Ω
    Q44-2 (E) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

REPLACE LICENSE PLATE LIGHT (RH SIDE)

15. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU RH - BODY GROUND)

  1. E108569E04
    Disconnect the RD main body ECU RH connector.

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    RD-1 (TRLY) - Body ground
    		 Always
    		 10 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


16. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU RH - BODY GROUND)

  1. E108569E04
    Connect the RD main body ECU RH connector.

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    RD-1 (TRLY) - Body ground
    		 Engine switch off
    		 Below 1 V
    RD-1 (TRLY) - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V



NG
REPLACE MAIN BODY ECU RH (COWL SIDE J/B RH)
OK


17. INSPECT MAIN BODY ECU LH (COWL SIDE J/B LH)

  1. E123262E02
    Disconnect the LJ main body ECU LH connector.

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    LJ-24 - Body ground
    		 Engine switch off
    		 Below 1 V
    LJ-24 - Body ground
    		 Engine switch on (IG) and taillights on
    		 10 to 14 V



NG
REPLACE MAIN BODY ECU LH (COWL SIDE J/B LH)
OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (MAIN BODY ECU LH - EACH REAR LIGHT)


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