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Home >> Toyota >> 2021 >> 4Runner TRD Pro >> Repair and Diagnosis >> Brakes >> Anti-Lock Brakes >> Vehicle Stability Control System (For Hydraulic Brake Booster) - Diagnostic Codes (43, C0226-C1422) >> VEHICLE STABILITY CONTROL SYSTEM (for Hydraulic Brake Booster) >> DTC C1379: Downhill Assist Control Switch Malfunction (Test Mode DTC) [08/2019 - ] >> Procedure

DTC C1379: Downhill Assist Control Switch Malfunction (Test Mode DTC) [08/2019 - ]: Procedure

  1. CONFIRM VEHICLE SPECIFICATIONS 
    1. Confirm the vehicle specifications.
      RESULT

      Result Proceed to
      w/ Downhill Assist Control A
      w/ Crawl Control B

    Result: 

    B 

    See step  6

    Result: 

    A 

    See step  2

  2. READ VALUE USING TECHSTREAM (DOWNHILL ASSIST CONTROL SW) 
    1. Turn the ignition switch off.
    2. Connect the Techstream to the DLC3.
    3. Turn the ignition switch to ON.
    4. Turn the Techstream on.
    5. Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.
    6. Check the Data List for proper functioning of the downhill assist control switch.
      ABS/VSC/TRAC

      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Downhill Assist Control SW Downhill assist control switch / ON or OFF ON: Downhill assist control on
      OFF: Downhill assist control off      		 -

      OK

      The Techstream displays ON or OFF according to downhill assist control switch operation.

    Result: 

    NG 

    See step  4

    Result: 

    OK 

    See step  3

  3. CHECK TEST MODE DTC 
    1. Perform the Downhill Assist Control Switch Check in the Test Mode Procedure (Refer to TEST MODE PROCEDURE [08/2019 - ] ).

      OK

      Test mode DTC C1379 is cleared.

    Result: 

    OK 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [08/2019 - ] 

    Result: 

    NG 

    REPLACE MASTER CYLINDER SOLENOID. Refer to  DISASSEMBLY [08/2015 - ] 

  4. INSPECT DOWNHILL ASSIST CONTROL SWITCH 

    Refer to PROCEDURE - Step 3

    Result: 

    NG 

    REPLACE DOWNHILL ASSIST CONTROL SWITCH. Refer to  REMOVAL [08/2015 - ] 

    Result: 

    OK 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - DOWNHILL ASSIST CONTROL SWITCH/BODY GROUND) 
    1. Disconnect the A6 skid control ECU connector.
    2. Disconnect the U8 downhill assist control switch connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A6-44 (HDCS) - U8-4 (+B2) Always Below 1 Ω
      A6-44 (HDCS) - Body ground Always 10 kΩ or higher
      U8-1 (E) - Body ground Always Below 1 Ω

    Result: 

    OK 

    REPLACE MASTER CYLINDER SOLENOID. Refer to  DISASSEMBLY [08/2015 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  6. CHECK CAN BUS 
    1. Check that there are no problems with the CAN communication system (Refer to DIAGNOSIS SYSTEM [08/2019 - 08/2021] , or refer to DIAGNOSIS SYSTEM [08/2021 - 08/2022] , or refer to DIAGNOSIS SYSTEM [08/2022 - ] ).

    Result: 

    NG 

    GO TO CAN COMMUNICATION SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING). Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [08/2019 - ] 

    Result: 

    OK 

    See step  7

  7. READ VALUE USING TECHSTREAM (CRAWL CONTROL MODE SELECT SWITCH) 
    1. Turn the ignition switch off.
    2. Connect the Techstream to the DLC3.
    3. Turn the ignition switch to ON.
    4. Turn the Techstream on.
    5. Enter the following menus: Body Electrical / D-SEAT SW / Data List.
    6. Check the Data List for proper functioning of the crawl control mode select switch.
      D-SEAT SW

      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Crawl Control Main Switch Crawl control switch (ON/OFF switch)/ ON or OFF ON: Crawl control on
      OFF: Crawl control off      		 -

      OK

      The Techstream displays ON or OFF according to crawl switch operation.

    Result: 

    NG 

    See step  10

    Result: 

    OK 

    See step  8

  8. READ VALUE USING TECHSTREAM (CRAWL CONTROL SWITCH) 
    1. Turn the ignition switch off.
    2. Connect the Techstream to the DLC3.
    3. Turn the ignition switch to ON.
    4. Turn the Techstream on.
    5. Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.
    6. Check the Data List for proper functioning of the crawl control switch.
      ABS/VSC/TRAC

      Tester Display Measurement Item/Range Normal Condition Diagnostic Note
      Crawl Control Switch Crawl switch (mode select switch)/ LOW, MIDLOW, MID, MIDHIGH or HIGH Actual crawl speed selector switch position -

      OK

      The Techstream displays LOW, MIDLOW, MID, MIDHIGH or HIGH according to crawl switch (mode selector switch) operation.

    Result: 

    NG 

    See step  11

    Result: 

    OK 

    See step  9

  9. CHECK TEST MODE DTC 
    1. Perform the crawl switch check in the Test Mode Procedure (Refer to TEST MODE PROCEDURE [08/2019 - ] ).

      OK

      Test mode DTC C1379 is cleared.

    Result: 

    OK 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [08/2019 - ] 

    Result: 

    NG 

    REPLACE MASTER CYLINDER SOLENOID. Refer to  DISASSEMBLY [08/2015 - ] 

  10. CHECK TERMINAL VOLTAGE AND RESISTANCE (IG, +B, GND) 
    1. Disconnect the U1 drive monitor switch connector.
    2. Measure the voltage according to the value(s) in the table below.
      GTY723624Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      U1-6 (+B) - Body ground Always 11 to 14 V
      U1-12 (IG) - Body ground Ignition switch ON 11 to 14 V
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      U1-7 (GND) - Body ground Always Below 1 Ω
      TEXT IN ILLUSTRATION

      *a Front view of wire harness connector
      (to Drive Monitor Switch)

    Result: 

    OK 

    REPLACE DRIVE MONITOR SWITCH. Refer to  REMOVAL [08/2015 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  11. REPLACE DRIVE MONITOR SWITCH 
    1. Replace the drive monitor switch (Refer to REMOVAL [08/2015 - ] ).

    Result: 

    NEXT 

    See step  12

  12. CHECK TEST MODE DTC 
    1. Perform the crawl switch check in the Test Mode Procedure (Refer to TEST MODE PROCEDURE [08/2019 - ] ).

      OK

      Test mode DTC C1379 is cleared.

    Result: 

    OK 

    END 

    Result: 

    NG 

    REPLACE MASTER CYLINDER SOLENOID. Refer to  DISASSEMBLY [08/2015 - ] 

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