Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC C1242 Rear Left Abs Sensor Signal: Trouble Symptom
2016 Subaru Legacy 2.5iSECTION Trouble Symptom
- ABS does not operate.
- VDC does not operate.
- Hill hold does not function.
- EyeSight does not operate. (Models with EyeSight)NOTE: This DTC may be stored when the wheel speed sensor connector is disconnected regardless of the ignition switch condition (ON/OFF). Perform the Clear Memory Mode after diagnosis if a DTC is recorded. < Ref. to CLEAR MEMORY MODE . >
DIAGNOSTIC PROCEDURE
| Step | Check | Yes | No |
|---|---|---|---|
1 CHECK OUTPUT OF ABS WHEEL SPEED SENSOR USING SUBARU SELECT MONITOR.
|
During acceleration/deceleration when the steering wheel is in the straight-ahead position, does the speed indicated on the data monitor change in response to the speedometer reading? In addition, are the wheel speed values of the freeze frame data for 4 wheels almost the same? | Go to step 2 . | Go to step 7 . |
| 2 CHECK POOR CONTACT OF CONNECTOR. Turn the ignition switch to OFF. |
Is there poor contact of connectors between VDCCM & H/U and ABS wheel speed sensor? | Repair the connector. | Go to step 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? | Go to step 4 . | 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? | Install the noise sources apart from sensor harness. | Go to step 5 . |
5 CHECK VDCCM & H/U.
|
Is the same DTC displayed? | Replace the VDCCM & H/U. < Ref. to VDC CONTROL MODULE AND HYDRAULIC CONTROL UNIT (VDCCM & H/U) . > | Go to step 6 . |
| 6 CHECK DETECTION OF OTHER DTCS FOR VDC. < Ref. to READ DIAGNOSTIC TROUBLE CODE (DTC) . > |
Is any other DTC displayed? | Perform the diagnosis according to DTC. < Ref. to LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . > | Currently, it is normal. There may have been a poor contact in the harness and connector or a temporarily noise interference. |
| 7 CHECK INSTALLATION OF ABS WHEEL SPEED SENSOR. | Is the ABS wheel speed sensor installation bolt tightened to 7.5 N.m (0.76 kgf-m, 5.5 ft-lb)? | Go to step 8 . | Tighten the ABS wheel speed sensor installation bolts. |
8 CHECK ABS WHEEL SPEED SENSOR SIGNAL.
|
Does the oscilloscope indicate the waveform pattern like shown in the figure when the tire is slowly turned? 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? | Go to step 10 . | Go to step 9 . |
| 9 CHECK ABS WHEEL SPEED SENSOR OR MAGNETIC ENCODER. | Are there foreign matter, breakage or damage at the tip of ABS wheel speed sensor or magnetic encoder? | 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. | Go to step 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? | Go to step 11 . | 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? | Install the noise sources apart from sensor harness. | Go to step 12 . |
12 CHECK VDCCM & H/U.
|
Is the same DTC displayed? | Go to step 13 . | Go to step 14 . |
13 CHECK FREEZE FRAME DATA OF ABS WHEEL SPEED SENSOR USING SUBARU SELECT MONITOR.
|
Is the ABS wheel speed sensor output different compared with other wheels? | Replace the ABS wheel speed sensor which has a difference. < Ref. to FRONT ABS WHEEL SPEED SENSOR . > < Ref. to REAR ABS WHEEL SPEED SENSOR . > | Replace the VDCCM & H/U. < Ref. to VDC CONTROL MODULE AND HYDRAULIC CONTROL UNIT (VDCCM & H/U) . > |
| 14 CHECK DETECTION OF OTHER DTCS FOR VDC. < Ref. to READ DIAGNOSTIC TROUBLE CODE (DTC) . > |
Is any other DTC displayed? | Perform the diagnosis according to DTC. < Ref. to LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . > | Currently, it is normal. There may have been a poor contact in the harness and connector or a temporarily noise interference.
NOTE:
Though the ABS warning light may remain on at this time, this is normal. Drive the vehicle at 40 km/h (25 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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RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.