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Home >> Lexus >> 2007 >> LX 470 >> Repair and Diagnosis >> Brakes >> Traction Control >> Brake Control >> Vehicle Stability Control System >> DTC C1256/56 Accumulator Low Pressure >> Inspection Procedure
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Inspection Procedure

  1. CHECK ACCUMULATOR OPERATION 
    1. Turn the ignition switch OFF, and depress the brake pedal 40 times or more.

      HINT:

      When pressure in power supply system is released, the brake pedal becomes easier to depress.

    2. Install the LSPV gauge (SST) to the rear brake caliper and bleed air.

      SST 09709-29018 

    3. Depress the brake pedal with force of more than 343 N (35 kgf, 77 lbf) and turn the ignition switch ON. Then check the rear brake caliper pressure when an increase of pressure changes from acutely to mildly.

      Standard pressure: 

      5,099 to 8,924 kPa (52 to 91 kgf/cm 2  , 740 to 1,294 psi) at 20°C (68°F) 

      HINT:

      If the value is not within the standard, cool the engine room and check it again.

    NG: REPLACE ACCUMULATOR 

    OK: Go to Next step 

  2. CHECK OPERATION BRAKE ACTUATOR PUMP MOTOR 
    1. Disconnect A43 and A44 actuator connectors.
    2. Connect the battery positive (+) lead to terminal 2 (BM1) or 3 (BM2) and battery negative (-) lead to terminal 1 (GND1) or 6 (GND2) of the brake actuator (pump motor).

      OK: Operation sound of pump motor should be heard. 

    NG: Go to step  7

    Fig 1: Identifying A43 And A44 Actuator Connectors Terminals
    G05283306Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    OK: Go to Next step 

  3. CHECK PRESSURE SWITCH (PH) OPERATION 
    1. Turn the ignition switch OFF, and depress the brake pedal 40 times or more.

      HINT:

      When pressure in power supply system is released, the brake pedal becomes easier to depress.

    2. Install the LSPV gauge (SST) to the rear brake caliper and bleed air.

      SST 09709-29018 

    3. While checking the voltage between terminals 3 (PH) and 5 (PHG) of the brake actuator, depress the brake pedal with force of more than 343 N (35 kgf, 77 lbf) and turn the ignition switch ON. Then check the rear wheel cylinder pressure when the voltage changes from 6 V to 0 V.

      Standard pressure: 

      12,553 to 20,104 kPa (128 to 205 kgf/cm 2  , 1,820 to 2,916 psi) 

      Fig 2: Identifying A43 Connector Terminals
      G05283295Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    4. Turn the ignition switch OFF and disconnect the connector A43 from the brake actuator.
    5. While checking the resistance between terminals 3 (PH) and 5 (PHG), depress the brake pedal while changing the force in the range of 197 N (20 kgf, 44 lbf) to 343 N (35 kgf, 77 lbf) and check the rear wheel cylinder pressure when the resistance changes from 0 kΩ to 1 kΩ between 3 (PH) and 5 (PHG).

      Standard pressure: 

      11,964 to 18,240 kPa (122 to 186 kgf/cm 2  , 1,735 to 2,645 psi) 

      HINT:

      After inspection, connect the connector, fill brake reservoir with brake fluid and clear the DTC.

    OK: Go to step  5

    NG: Go to Next step 

  4. CHECK WIRE HARNESS (SKID CONTROL ECU ASSEMBLY - BRAKE ACTUATOR) 

    NG: REPAIR OR REPLACE HARNESS AND CONNECTOR 

    OK: REPLACE BRAKE ACTUATOR 

  5. CHECK PRESSURE SWITCH (PL) OPERATION 
    1. Turn the ignition switch OFF, and depress the brake pedal 40 times or more.

      HINT:

      When pressure in power supply system is released, the brake pedal becomes easier to depress.

    2. Install the LSPV gauge (SST) to the rear brake caliper and bleed air.

      SST 09709-29018 

    3. Disconnect the connector A44 from the brake actuator.
    4. While checking the voltage between terminals 4 (PL) and 2 (PLG) of the brake actuator, depress the brake pedal with force of more than 343 N (35 kgf, 77 lbf) and turn the ignition switch ON. Then check the rear wheel cylinder pressure when the resistance changes from 5.7 kΩ to 1.0 kΩ.

      Standard pressure: 

      9,022 to 15,102 kPa (92 to 154 kgf/cm 2  , 1,308 to 2,190 psi) 

      Fig 3: Identifying A44 Connector Terminals
      G05283308Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    5. Turn the ignition switch OFF and disconnect the connector A44 from the brake actuator.
    6. While checking the resistance between terminals 4 (PL) and 2 (PLG) of the brake actuator, depress the brake pedal while changing the force in the range of 197 N (20 kgf, 44 lbf) to 343 N (35 kgf, 77 lbf) and check the rear wheel cylinder pressure when the resistance changes from 1.0 kΩ to 5.7 kΩ.

      Standard pressure: 

      8,532 to 13,337 kPa (87 to 136 kgf/cm 2  , 1,237 to 1,934 psi) 

      HINT:

      After inspection, connect the connector, fill brake reservoir with brake fluid and clear the DTC.

    NG: REPLACE BRAKE ACTUATOR 

    OK: Go to Next step 

  6. CHECK PRESSURE SWITCH (PH) AND PRESSURE SWITCH (PL) 
    1. Compare the pressure value of the rear wheel cylinder measured in check pressure switch (PL) operation with the one measured in check pressure switch (PH) operation.

      OK: Pressure when the voltage between PH and PHG becomes 0 to 6 V is greater than pressure when the resistance between PL and PLG becomes 1.0 to 5.7 kΩ 

      Pressure when the resistance between PH and PHG becomes 0 to 1 kΩ is greater than pressure when the resistance between PL and PLG becomes 1.0 to 5.7 kΩ 

    NG: REPLACE BRAKE ACTUATOR 

    OK: REPLACE SKID CONTROL ECU ASSEMBLY 

  7. CHECK BRAKE CONTROL WIRE 

    NG: REPLACE BRAKE CONTROL WIRE 

    OK: Go to Next step 

  8. CHECK BRAKE ACTUATOR PUMP MOTOR 

    NG: REPLACE BRAKE ACTUATOR PUMP MOTOR 

    OK: REPLACE BRAKE ACTUATOR 

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