ABS Wheel Speed Sensor - Front

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

Warnings

Tools required

Parts

• Front ABS wheel speed sensor × 1 — A2215400317 or A2215400417 (verify left/right)
• Sensor mounting bolt × 1 — Use OEM specification

Preparation

1. Use diagnostic scanner to confirm which front wheel speed sensor has failed (left or right side)
2. Park vehicle on level surface and engage parking brake
3. Place wheel chocks behind rear wheels
4. Loosen front wheel lug nuts while vehicle is on ground
5. Raise front of vehicle and support securely on jack stands at designated lift points
6. Remove front wheel on affected side

Procedure

1. 1

   Locate ABS sensor
   Locate the ABS wheel speed sensor mounted on the steering knuckle behind the brake rotor. The sensor is positioned near the top of the knuckle with a wire harness running up toward the wheel well. On the S65 AMG, the sensor is typically secured with a single 8mm bolt.
2. 2

   Disconnect electrical connector
   Follow the sensor wire harness upward into the wheel well area. Locate the electrical connector (typically 10-15 inches from sensor). Press the release tab and carefully disconnect the connector. Note the routing of the wire harness for reinstallation.
3. 3

   Remove wire harness clips
   Release any wire harness retention clips or brackets securing the sensor wire along the suspension components or wheel well. Use a plastic pry tool to avoid damaging clips. There are typically 1-2 clips between the sensor and connector.
4. 4

   Remove sensor mounting bolt
   Using an 8mm socket or wrench, carefully remove the ABS sensor mounting bolt from the steering knuckle. If the bolt is corroded, apply penetrating oil and allow to soak for 5-10 minutes. Keep the bolt if in good condition or replace with new.
   Torque spec

   ABS Sensor Bolt10 Nm (7 lb-ft)
5. 5

   Extract ABS sensor
   Carefully pull the ABS sensor straight out from the steering knuckle bore. Do not twist or pry against the sensor body. If sensor is stuck due to corrosion, gently wiggle while pulling outward. Avoid using excessive force that could damage the knuckle bore or tone ring.
   ⚠Do not use metal tools to pry the sensor out as this can damage the tone ring on the wheel bearing hub.
6. 6

   Clean sensor bore
   Use a wire brush to clean the sensor mounting bore in the steering knuckle. Remove all rust, dirt, and debris. The bore must be clean for proper sensor seating and accurate gap between sensor tip and tone ring. Spray electrical contact cleaner into bore and wipe clean.
7. 7

   Inspect tone ring
   Visually inspect the tone ring (reluctor ring) on the wheel bearing hub for damage, missing teeth, or excessive rust buildup. Clean the tone ring surface if necessary using a soft brush. Any damage to the tone ring will cause continued ABS faults even with new sensor.
   ⚠Do not clean tone ring with aggressive tools or solvents that could damage the magnetic pattern or teeth.
8. 8

   Prepare new sensor
   Remove new ABS sensor from packaging. Compare with old sensor to verify correct part. Apply a thin layer of dielectric grease to the sensor O-ring (if equipped) and tip area to prevent corrosion and aid future removal. Do not apply grease to the actual sensing tip.
9. 9

   Install new sensor
   Insert the new ABS sensor straight into the steering knuckle bore until it seats fully. The sensor should slide in smoothly without force. Ensure the sensor is completely seated against the mounting surface before installing bolt. Align the mounting hole.
10. 10

    Install and torque mounting bolt
    Install the ABS sensor mounting bolt and hand-tighten. Using a torque wrench, tighten the bolt to exactly 10 Nm (7 lb-ft). This is a critical specification - overtightening can strip the aluminum threads in the knuckle or crack the sensor body.
    ⚠Do not exceed 10 Nm torque. The mounting hole threads are easily stripped.
    Torque spec

    ABS Sensor Bolt10 Nm (7 lb-ft)
11. 11

    Route and secure wire harness
    Route the sensor wire harness following the original path along the suspension components. Ensure adequate slack for suspension travel and steering movement. Secure all wire harness clips and brackets. The harness must not contact rotating components or sharp edges.
12. 12

    Connect electrical connector
    Reconnect the electrical connector to the ABS sensor wire harness. Ensure the connector clicks fully into place and the locking tab engages. Gently tug on the connection to verify it is secure.
13. 13

    Reinstall wheel
    Reinstall the front wheel onto the hub. Install all lug nuts and hand-tighten in a star pattern. Lower the vehicle until the tire just contacts the ground to prevent wheel rotation. Torque lug nuts to specification in a star pattern.
    Torque spec

    Wheel Lug Nuts183 Nm (135 lb-ft)

Reassembly

1. Lower vehicle completely and remove jack stands
2. Perform final torque check on wheel lug nuts with vehicle on ground
3. Start engine and verify ABS warning light extinguishes after initial self-test (approximately 3-5 seconds)

Verification

• Use diagnostic scanner to clear ABS fault codes and verify no new codes are present
• Perform test drive at speeds above 15 mph to allow ABS system to complete self-check
• Verify ABS warning light remains off during and after test drive
• Perform gentle ABS activation test in safe area (if qualified) to confirm proper sensor operation
• Re-scan for codes after test drive to confirm repair success

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