ABS Wheel Speed Sensor - Rear

Replace the rear ABS wheel speed sensor to restore proper anti-lock brake system functionality and eliminate ABS warning lights.

Warnings

Tools required

Parts

• Rear ABS wheel speed sensor × 1 — A0009059102 or A0009059202 (side-specific)
• ABS sensor mounting bolt × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Place wheel chocks in front of front wheels
3. Lift rear of vehicle and secure on jack stands at proper jacking points
4. Remove rear wheel on the side requiring sensor replacement

Procedure

1. 1

   Access the ABS sensor connector
   Locate the ABS wheel speed sensor electrical connector inside the rear wheel well. It is typically secured to a bracket near the control arm or shock absorber mounting area. Release the connector locking tab and disconnect the sensor harness.
2. 2

   Remove sensor wire routing clips
   Trace the sensor wire from the connector to the sensor body. Carefully release any plastic routing clips or brackets securing the wire to the suspension components or body. Note the exact routing path for reinstallation.
3. 3

   Remove the old ABS sensor mounting bolt
   Locate the ABS sensor mounted to the rear wheel bearing carrier or knuckle. Using a 10mm socket, carefully remove the single mounting bolt securing the sensor. The bolt may be corroded; apply penetrating oil if necessary and allow to soak before removal.
   Torque spec

   ABS Sensor Bolt10 Nm (7 lb-ft)
4. 4

   Extract the old sensor
   Gently pull the sensor straight out of its mounting bore in the wheel bearing carrier. If the sensor is stuck due to corrosion, carefully wiggle it while pulling. Do not pry against the sensor body or tone ring. If extremely stuck, use a small amount of penetrating oil around the base and allow to soak.
5. 5

   Clean the sensor mounting bore
   Use a wire brush to thoroughly clean the sensor mounting bore in the wheel bearing carrier. Remove all corrosion, dirt, and debris. Ensure the bore is clean and smooth to allow proper sensor seating. Inspect the tone ring on the bearing for damage, cracks, or missing teeth.
6. 6

   Prepare the new sensor
   Remove the new sensor from packaging and inspect for damage. Apply a thin coat of high-temperature anti-seize compound or dielectric grease to the sensor body O-ring and mounting surface (not the sensor tip). Clean the electrical connector with electrical contact cleaner.
7. 7

   Install the new sensor
   Insert the new ABS sensor straight into the mounting bore, ensuring it is fully seated against the wheel bearing carrier. Align the mounting hole in the sensor bracket with the threaded hole in the carrier. Hand-thread the new mounting bolt to prevent cross-threading.
8. 8

   Torque the sensor mounting bolt
   Using a torque wrench and 10mm socket, tighten the ABS sensor mounting bolt to exactly 10.0 Nm (7.0 lb-ft). Do not exceed this specification as the bolt threads into aluminum and can strip if overtightened. Verify the sensor is firmly seated and does not rotate.
   Torque spec

   ABS Sensor Bolt10 Nm (7 lb-ft)
9. 9

   Route and secure the sensor harness
   Route the sensor wire following the exact path noted during removal. Secure the wire to all original mounting clips and brackets. Ensure the wire has no sharp bends, is not stretched tight, and will not contact any moving suspension components or the tire.
10. 10

    Connect the electrical connector
    Connect the sensor harness to the vehicle wiring connector. Ensure the connector locks securely with an audible click. Gently tug on the connection to verify it is properly seated. Secure the connector to its mounting bracket if applicable.
11. 11

    Reinstall the wheel
    Mount the rear wheel onto the hub, ensuring it seats properly on the centering ring. Hand-thread all lug nuts to prevent cross-threading. Lower the vehicle slightly so the wheel contacts the ground but still has most weight on the jack stands.
12. 12

    Torque wheel lug nuts
    Using a torque wrench, tighten the wheel lug nuts to 183.0 Nm (135.0 lb-ft) in a star pattern to ensure even seating. Fully lower the vehicle to the ground and remove jack stands. Perform a final torque check of all lug nuts with the vehicle weight on the wheels.
    Torque spec

    Wheel Lug Nuts183 Nm (135 lb-ft)

Reassembly

1. Ensure sensor wire routing does not interfere with suspension travel or tire rotation
2. Verify electrical connector is fully locked and secured to bracket
3. Double-check wheel lug nut torque after lowering vehicle

Verification

• Start the engine and verify the ABS warning light extinguishes after initial self-test (usually 3-5 seconds)
• Use a Mercedes-Benz diagnostic scanner (XENTRY or compatible) to verify the new sensor is transmitting data and no fault codes are present
• Perform a slow test drive (under 25 mph) and verify the ABS system recognizes wheel speed from the replaced sensor
• Check for proper sensor clearance by rotating the wheel by hand and listening for any rubbing or contact noise
• Recheck diagnostic codes after test drive to confirm no new faults have appeared

Related trouble codes on this vehicle

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