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Home >> Subaru >> 2017 >> Forester 2.0XT Touring >> Repair and Diagnosis >> Brakes >> Brakes Control Systems >> Brake Control System (Diagnostics) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC C1242 Rear Left Abs Sensor Signal >> Trouble symptom

DTC C1242 Rear Left Abs Sensor Signal: Trouble symptom

  1. CHECK ABS WHEEL SPEED SENSOR AND FREEZE FRAME DATA USING SUBARU SELECT MONITOR. 
    1. Using the Subaru Select Monitor, check the freeze frame data when DTC is detected. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Subaru Select Monitor>OPERATION>FREEZE FRAME DATA .
    2. Compare [FR Wheel Speed], [FL Wheel Speed], [RR Wheel Speed] and [RL Wheel Speed] to determine a sensor that is not indicating the same value.
    3. Check the data monitor of the wheel speed sensor that is not indicating the same value. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Subaru Select Monitor>OPERATION>DATA MONITOR .

    Does the speed indicated on the current data change in response to the speedometer reading during acceleration/deceleration when the steering wheel is in the straight-ahead position? And, are the values on the freeze frame data of the vehicle speed from the four wheels indicated as almost identical?

    • Yes  : Go to 2. 
    • No  : Go to  7.
  2. CHECK POOR CONTACT OF CONNECTOR. 
    1. Turn the ignition switch to OFF.
    2. Check for poor contact of the connector between VDCCM&H/U and ABS wheel speed sensor.

    Is there poor contact of connectors between VDCCM&H/U and ABS wheel speed sensor?

    • Yes  : Repair the connector.
    • No  : Go to 3. 
  3. CHECK CAUSE OF SIGNAL NOISE. 

    Make sure the radio wave devices and electronic components are installed correctly.

    Are the radio wave devices and electronic components installed correctly?

    • Yes  : Go to 4. 
    • No  : Install the radio wave devices and electronic components properly.
  4. CHECK CAUSE OF SIGNAL NOISE. 

    Check if the noise sources (such as an antenna) are installed near the sensor harness.

    Are noise sources installed?

    • Yes  : Install the noise sources apart from sensor harness.
    • No  : Go to 5. 
  5. CHECK VDCCM&H/U. 
    1. Connect all connectors.
    2. Clear the memory. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Clear memory .
    3. Perform the Inspection Mode. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Inspection Mode .
    4. Read the DTC. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

    Is the same DTC displayed?

  6. CHECK DETECTION OF OTHER DTCS FOR VDC. 

    Ref. to BRAKE CONTROL (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

    Is any other DTC displayed?

  7. CHECK INSTALLATION OF ABS WHEEL SPEED SENSOR. 

    Are the ABS wheel speed sensor installation bolts tightened to 7.5 N.m (0.76 kgf-m, 5.5 ft-lb)?

    • Yes  : Go to 8. 
    • No  : Tighten the ABS wheel speed sensor installation bolts.
  8. CHECK ABS WHEEL SPEED SENSOR SIGNAL. 
    1. Prepare an oscilloscope.
    2. Check the ABS wheel speed sensor. Ref. to VEHICLE DYNAMICS CONTROL (VDC)>Front ABS Wheel Speed Sensor>INSPECTION>CHECK ABS WHEEL SPEED SENSOR UNIT . Ref. to VEHICLE DYNAMICS CONTROL (VDC)>Rear ABS Wheel Speed Sensor>INSPECTION>CHECK ABS WHEEL SPEED SENSOR UNIT .

    Does the oscilloscope indicate the waveform pattern as shown in the figure when the tires are turning? Or does the oscilloscope indication repeat the waveform pattern like shown in the figure when the tire is slowly turned in equal speed for one rotation or more?

    • Yes  : Go to  10.
    • No  : Go to 9. 
  9. CHECK ABS WHEEL SPEED SENSOR OR MAGNETIC ENCODER. 

    Are there foreign matters adhered to the tip of ABS wheel speed sensor or magnetic encoder? Or is there any breakage or damage?

    • Yes  : Remove dirt thoroughly. Also replace the ABS wheel speed sensor or magnetic encoder as a unit with hub unit bearing if it is broken or damaged.
    • No  : Go to 10. 
  10. CHECK CAUSE OF SIGNAL NOISE. 

    Make sure the radio wave devices and electronic components are installed correctly.

    Are the radio wave devices and electronic components installed correctly?

    • Yes  : Go to 11. 
    • No  : Install the radio wave devices and electronic components properly.
  11. CHECK CAUSE OF SIGNAL NOISE. 

    Check if the noise sources (such as an antenna) are installed near the sensor harness.

    Are noise sources installed?

    • Yes  : Install the noise sources apart from sensor harness.
    • No  : Go to 12. 
  12. CHECK VDCCM&H/U. 
    1. Connect all connectors.
    2. Clear the memory. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Clear memory .
    3. Perform the Inspection Mode. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Inspection Mode .
    4. Read the DTC. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

    Is the same DTC displayed?

    • Yes  : Go to 13. 
    • No  : Go to  14.
  13. CHECK FREEZE FRAME DATA OF ABS WHEEL SPEED SENSOR USING SUBARU SELECT MONITOR. 
    1. Using the Subaru Select Monitor, select Freeze frame data. Ref. to BRAKE CONTROL (DIAGNOSTICS)>Subaru Select Monitor>OPERATION>FREEZE FRAME DATA .
    2. Read the ABS wheel speed sensor output.

    Is the ABS wheel speed sensor output different compared with other wheels?

  14. CHECK DETECTION OF OTHER DTCS FOR VDC. 

    Ref. to BRAKE CONTROL (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

    Is any other DTC displayed?

    • Yes  : Perform the diagnosis according to DTC. Ref. to BRAKE CONTROL (DIAGNOSTICS)>List of Diagnostic Trouble Code (DTC) .
    • No  : Currently, it is normal. There may have been a temporary poor contact in the harness and connector or a temporary noise interference.
      NOTE: Though the ABS warning light may remain on at this time, this is normal. Drive the vehicle at 60 km/h (37 MPH) or more in order to turn ABS warning light off. Be sure to drive the vehicle and check that the warning light goes off.
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