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Home >> Toyota >> 2020 >> RAV4 LE, AWD >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Electronically Controlled Brake System (W/O Vacuum Brake Booster) - Diagnostic Codes (5 Of 8) >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (w/o Vacuum Brake Booster) >> DTC C1311: Open Circuit in Main Relay 1; DTC C1312: Short Circuit in Main Relay 1 [02/2019 - 12/2021] >> Procedure

DTC C1311: Open Circuit in Main Relay 1; DTC C1312: Short Circuit in Main Relay 1 [02/2019 - 12/2021]: Procedure

  1. PERFORM ACTIVE TEST USING TECHSTREAM (ABS MAIN RELAY) 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to ON.
    3. Select the Active Test on the Techstream.

      Refer to DATA LIST / ACTIVE TEST [02/2019 - 12/2021]

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      ECB Main Relay ABS main relay Relay ON/OFF ECB: Electronically Controlled Brake System

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display
      ECB Main Relay
    4. Select the Data List on the Techstream.

      Refer to DATA LIST / ACTIVE TEST [02/2019 - 12/2021]

      Chassis > ABS/VSC/TRAC > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      ECB Main Relay ABS main relay ON or OFF ON: Relay on
      OFF: Relay off      		 ECB: Electronically Controlled Brake System

      Chassis > ABS/VSC/TRAC > Data List 

      Tester Display
      ECB Main Relay
    5. Check that the condition of the ABS main relay observed on the Techstream changes according to the Techstream operation.

      Result

      Result Proceed to
      ABS main relay in the Data List turns ON/OFF using the Active Test. A
      ABS main relay in the Data List does not change using the Active Test. B

    Result: 

    B 

    See step  4

    Result: 

    A 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (BS TERMINAL) 
    1. Turn the ignition switch off.
      GTY937713Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))
    2. Make sure that there is no looseness at the locking part and the connecting part of the connector.
    3. Disconnect the A42 skid control ECU (brake booster with master cylinder assembly) connector.
    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A42-15 (BS) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BS CIRCUIT) 

    Result: 

    OK 

    See step  3

  3. RECONFIRM DTC 
    1. Reconnect the A42 skid control ECU (brake booster with master cylinder assembly) connector.
    2. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [02/2019 - 12/2021]

      Chassis > ABS/VSC/TRAC > Clear DTCs 

    3. Turn the ignition switch off.
    4. Turn the ignition switch to ON.
    5. Check if the same DTC is output.

      Refer to DTC CHECK / CLEAR [02/2019 - 12/2021]

      Chassis > ABS/VSC/TRAC > Trouble Codes 

      Result

      Result Proceed to
      DTCs C1311 and C1312 are not output. A
      DTCs C1311 and/or C1312 are output. B

    Result: 

    A 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2018 - ] 

    Result: 

    B 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [02/2019 - 10/2019]  , or refer to  REMOVAL [10/2019 - 08/2020]  , or refer to  REMOVAL [08/2020 - 12/2021] 

  4. CHECK HARNESS AND CONNECTOR (BI TERMINAL) 
    1. Turn the ignition switch off.
      GTY890579Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))
    2. Make sure that there is no looseness at the locking part and the connecting part of the connector.
    3. Disconnect the A42 skid control ECU (brake booster with master cylinder assembly) connector.
    4. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A42-14 (BI) - Body ground Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BI CIRCUIT) 

    Result: 

    OK 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (BS TERMINAL) 
    1. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A42-15 (BS) - Body ground Always 11 to 14 V
      GTY937713Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [02/2019 - 10/2019]  , or refer to  REMOVAL [10/2019 - 08/2020]  , or refer to  REMOVAL [08/2020 - 12/2021] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (BS CIRCUIT) 

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