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Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 472 (Gateway System - Diagnosis) >> Circuit Inspection >> DTC B1291, B1292: Light system communication bus malfunction (+B short), Light system communication bus malfunction (GND short) >> Inspection Procedure

Inspection Procedure

WARNING: This page is about a different car, the 2003 Lexus LS 430. However, it is still accessible from the selected car via links, so may be relevant.
  1. Check communication circuit inside ECU. 

    PREPARATION: 

    Disconnect the following connectors of ECU in order from the top downward.

    HINT:

    Before disconnecting the next connector, be sure that removed ECU connector is reconnected.

    DTC DETECTION ITEM

    Disconnect ECU connector Connector No.
    Front light ECU -
    Luggage room J/B ECU L14
    Clearance sonar ECU C17
    Combination switch C14
    Power tilt and power telescopic ECU P8
    Steering pad switch C13
    Driver side J/B ECU D3, D5
    Fig 1: Checking Continuity Of Wire Harness Between Connectors
    G03376594Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    CHECK: 

    Check the DTC every time each connector is disconnected.

    OK: 

    DTC B1291 or B1292 is not output.

    1. OK : Replace corresponding ECU (ECU for which DTC is deleted is defective.) (See  HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE  ). 
    2. NG : Go to next step. 
  2. Check for short circuit between ECUs. 

    PREPARATION: 

    Disconnect the following pairs of ECU connectors simultaneously, from the top downward.

    HINT:

    • Before disconnecting the next connector, be sure that disconnected ECU connector is reconnected.
    • The short circuit check can be performed on the circuit by disconnecting it from the MPX communication bus circuit

      If DTC is deleted, this means that the circuit being checked is short-circuited and it must be repaired

      DTC DETECTION ITEM

      Disconnect ECU connector Connector No.
      Front light ECU
      Driver side J/B ECU      		 -
      D3
      Luggage room J/B ECU
      Combination switch      		 L14
      C14
      Luggage room J/B ECU
      Clearance sonar ECU      		 L14
      C17
      Combination switch
      Power tilt and power telescopic ECU      		 C14
      P8
      Power tilt and power telescopic ECU
      Driver side J/B ECU      		 P8
      D5
      Driver side J/B ECU
      Steering pad switch      		 D5
      C13
      Fig 2: Checking Continuity Of Wire Harness Between Connectors
      G03376595Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    CHECK: 

    Check the DTC every time a pair of connectors are disconnected.

    OK: 

    DTC B1291 or B1292 is not output.

    1. OK : Repair or replace corresponding wire harness. 
    2. NG : Go to next step. 
  3. Check for short circuit. 

    PREPARATION: 

    Disconnect the following ECU connectors.

    HINT:

    Before disconnecting the next connector, be sure that disconnected ECU connector is reconnected.

    DTC DETECTION ITEM

    Disconnect ECU connector Connector No.
    Gateway ECU
    Front light ECU    		 G3
    -
    Gateway ECU
    Luggage room J/B ECU    		 G3
    L14
    Fig 3: Checking Continuity Of Wire Harness Between Connectors
    G03376596Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    CHECK: 

    Check whether or not there is +B short and GND short between the above connector.

    OK: 

    No +B short and GND short. 

    1. NG : Repair or replace corresponding wire harness between (See  HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE  ). 
    2. OK : Replace gateway ECU (See  HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE  ). 
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