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VEHICLE STABILITY CONTROL SYSTEM (for Vacuum Brake Booster), Diagnostic DTC:C0278, C0279

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DTC Code DTC Name
C0278 Open in ABS Solenoid Relay Circuit
C0279 Short in ABS Solenoid Relay Circuit
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DESCRIPTION

The solenoid relay supplies power to the solenoid and TRC solenoid.

The solenoid relay is turned on 1.5 seconds after the ignition switch is turned to ON, and is turned off if an open or short in the solenoid is detected by the self diagnosis performed when the engine starts running.

The solenoid relay is housed in the skid control ECU in the actuator assembly.

On vehicles equipped with the Stop and Start System, DTC may be output if there is a significant difference between IG power source voltage and backup boost converter power source voltage when the stop and start system is cranking the engine during restarting.

DTC Code DTC Detection Condition Trouble Area
C0278

Either condition is met:


  1. Both of the following conditions continue for 0.22 seconds or more.


    • The IG1 terminal voltage is 9.5 V or higher.

    • The solenoid relay contact is open when the relay is on.

  3. Both conditions are met for 0.22 seconds or more.


    • The IG1 terminal voltage becomes below 9.5 V when the relay is turned on.

    • The relay contact remains open.

  • ABS NO. 2 fuse

  • Solenoid relay circuit

  • Brake actuator assembly (Solenoid relay)
C0279 Immediately after the ignition switch is turned to ON, the solenoid relay contact is closed for 4 seconds when the relay is turned off.

  • Solenoid relay circuit

  • Brake actuator assembly (Solenoid relay)
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WIRING DIAGRAM

Refer to DTCs C0226, C0236, C0246, C0256 and C1225 (Click here).

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INSPECTION PROCEDURE

Note:

  • When replacing the brake actuator assembly, perform calibration (Click here).

  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.

Tip:

When DTC C1241 is output together with DTC C0278 and/or C0279, inspect and repair the trouble areas indicated by DTC C1241 first (Click here).

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PROCEDURE


  1. Click here

    CHECK TERMINAL VOLTAGE (+BS)


    1. Turn the ignition switch off.

    2. Disconnect the A6 skid control ECU connector.

    3. A01DMHLE06

      Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A6-12 (+BS) - Body ground Always 11 to 14 V
      Table 1. Text in Illustration
      *a

      Front view of wire harness connector

      (to Skid Control ECU)

  2. Click here

    CHECK HARNESS AND CONNECTOR (GND1 TERMINAL)


    1. Disconnect the A6 skid control ECU connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      A6-1 (GND1) - Body ground Always Below 1 Ω

  3. Click here

    RECONFIRM DTC

    Tip:

    This code is stored when a problem is identified in the brake actuator assembly.

    The solenoid circuit is in the brake actuator assembly.

    Therefore, solenoid circuit inspections and solenoid unit inspections cannot be performed. Be sure to check if the DTC is output before replacing the brake actuator assembly.


    1. Reconnect the skid control ECU connector.

    2. Clear the DTCs (Click here).

    3. Start the engine.

    4. Drive the vehicle at a speed of 20 km/h (12 mph) or more for 30 seconds or more.

    5. Check if the same DTC is output (Click here).

      Table 2. Result
      Result Proceed to
      DTC not output A
      DTC output B
      Tip:

      • If a speed signal of 6 km/h (4 mph) or more is input to the skid control ECU with the ignition switch ON and the stop light switch off, the ECU performs self-diagnosis of the motor and solenoid circuits.

      • If the normal system code is output (the trouble code is not output), slightly jiggle the connectors, wire harnesses, and fuses of the brake actuator assembly. Make sure that no DTCs are output.

      • If any DTCs are output while jiggling a connector or wire harness of the brake actuator assembly (skid control ECU), inspect and repair the connector or wire harness. The DTCs were probably output due to a bad connection of the connector terminal.


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    USE SIMULATION METHOD TO CHECKClick here

  5. Click here

    REPAIR OR REPLACE HARNESS OR CONNECTOR (+BS CIRCUIT)

  6. Click here

    REPAIR OR REPLACE HARNESS OR CONNECTOR (GND1 CIRCUIT)

  7. Click here

    REPLACE BRAKE ACTUATOR ASSEMBLYClick here