LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2007 >> GS 450h >> Repair and Diagnosis >> Brakes >> Traction Control >> Brake Control >> Electronically Controlled Brake System >> DTC C1378/44 Capacitor Communication Malfunction >> Inspection Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Inspection Procedure

NOTE: When replacing the skid control ECU, perform initialization of linear solenoid valve and calibration (see INITIALIZATION  ).
  1. INSPECT BRAKE CONTROL POWER SUPPLY 
    1. Disconnect the U27 power supply connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard voltage 

      TESTER CONNECTION SPECIFIED CONDITION

      Tester Connection Specified Condition
      U27-5 (IG1) - Body ground 10 to 14 V
    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance 

      TESTER CONNECTION SPECIFIED CONDITION

      Tester Connection Specified Condition
      U27-14 (GND) - Body ground Below 1 Ω
      Fig 1: Identifying U27 Connector Terminals
      G05306001Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR (IG1 OR GND CIRCUIT) 

    OK: GO TO Next Step 

  2. CHECK WIRE HARNESS (SKID CONTROL ECU - BRAKE CONTROL POWER SUPPLY) 
    1. Disconnect the A13 ECU connector.
    2. Disconnect the U27 power supply connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance 

      TESTER CONNECTION SPECIFIED CONDITION

      Tester Connection Specified Condition
      A13-8 (ENA) - U27-12 (ENA) Below 1 Ω
      A13-23 (FAIL) - U27-13 (FAIL) Below 1 Ω
      A13-8 (ENA) - Body ground 10 kΩ or higher
      A13-23 (FAIL) - Body ground 10 kΩ or higher
      Fig 2: Identifying A13 And U27 Connectors Terminals
      G05306002Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: GO TO Next Step 

  3. RECONFIRM DTC 
    1. Clear the DTC (see DTC CHECK / CLEAR  ).
    2. Turn the power switch ON (IG).
    3. Check if the same DTC is recorded (see DTC CHECK / CLEAR  ).

      HINT:

      Reinstall the sensor, connectors, etc. and restore the vehicle to its prior condition before rechecking for DTCs.

      Result 

      RESULT

      Condition Proceed to
      DTC (C1378/44) is not output A
      DTC (C1378/44) is output B

    B:  GO TO step 4

    A: END 

  4. CHECK FREEZE FRAME DATA 
    1. Check the information code from the "FREEZE FRAME DATA " memorized when the DTC (C1378/44) is stored.

      Result 

      RESULT

      Condition Proceed to
      Information code is not output A
      Information code (112) is output B

    B: REPLACE BRAKE CONTROL POWER SUPPLY (See  REMOVAL   ) 

    A: REPLACE SKID CONTROL ECU (See  REMOVAL   ) 

scientia non olet · About LEMON Manuals