ABS Wheel Speed Sensor - Front

This procedure covers the removal and installation of a front ABS wheel speed sensor on a 2019 Mercedes-Benz G-Class with 4.0L Turbo V8 engine.

Warnings

Tools required

Parts

• Front ABS wheel speed sensor × 1 — Use OEM specification
• Plastic zip ties (for harness routing) × 2 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Place wheel chocks behind rear wheels
3. Loosen front wheel lug nuts 1/4 turn while vehicle is on ground
4. Raise front of vehicle with floor jack at designated front lift point
5. Support vehicle securely on jack stands at manufacturer's specified jacking points
6. Remove front wheel completely

Procedure

1. 1

   Locate the wheel speed sensor
   The front wheel speed sensor is mounted to the front steering knuckle (spindle) at the solid front axle end, behind the brake rotor. The sensor head inserts into the knuckle bore and the wiring harness routes upward toward the inner fender well. Visually identify the sensor body and its electrical connector before proceeding.
2. 2

   Disconnect the electrical connector
   Follow the sensor wiring harness from the sensor body to the electrical connector, typically located near the inner fender liner or strut tower area. Press the release tab on the connector and pull the connector halves apart. If the connector is secured with a secondary lock, slide the lock tab out first. Do not pull on the wires themselves.
3. 3

   Release harness routing clips
   The sensor harness is secured to the vehicle with routing clips or zip ties along the strut, brake line, or inner fender. Carefully release each clip by pressing the release tabs or cut zip ties with diagonal cutters. Note the exact routing path for reinstallation. Ensure sufficient slack is available to allow sensor removal.
4. 4

   Remove sensor mounting fastener
   Locate the single fastener securing the wheel speed sensor to the steering knuckle. Verify the exact fastener type and size (Torx or hex head) against W463 service documentation before removal. Remove the bolt completely and set aside. If the fastener shows corrosion or thread damage, replace it during reassembly.
5. 5

   Extract the wheel speed sensor
   Carefully pull the sensor straight out of its bore in the steering knuckle. The sensor may be held by corrosion or debris. If resistant, gently twist the sensor body while pulling. Do not pry against the sensor body or use excessive force. If the sensor is seized, apply penetrating oil around the sensor perimeter and allow 10-15 minutes for penetration before attempting removal again.
6. 6

   Clean the sensor bore
   Inspect the sensor bore in the steering knuckle. Use a wire brush to remove any rust, debris, or metallic particles from the bore. Spray electrical contact cleaner into the bore to flush out contamination. Ensure the bore is clean and dry before installing the new sensor. Inspect the tone ring (toothed reluctor ring) on the hub assembly for damage or excessive metallic buildup.
7. 7

   Install the new wheel speed sensor
   Verify the new sensor matches the old unit in physical dimensions and connector type. Do not apply anti-seize or grease to the sensor unless specified by Mercedes. Install the sensor dry (or with a manufacturer-approved lubricant only) to avoid attracting metallic debris to the sensing tip. Insert the new sensor straight into the knuckle bore, ensuring proper alignment. Push the sensor fully into the bore until it seats completely. The sensor tip should be positioned at the correct air gap from the tone ring (self-adjusting on this platform).
8. 8

   Install sensor mounting fastener
   Install the mounting bolt and hand-tighten. Torque the mounting bolt to the Mercedes-specified value (typically approximately 8-10 Nm / 6-7 lb-ft for a small M6 sensor bolt — verify against W463 documentation). Verify the sensor body is fully seated and does not rotate after torquing.
   Torque spec

   Caliper Mounting Bolts101 Nm (75 lb-ft)
9. 9

   Route and secure the wiring harness
   Route the sensor harness along the original path noted during removal. Ensure the harness does not contact the brake rotor, suspension arms, or steering components throughout full suspension travel and steering lock-to-lock. Secure the harness using new plastic zip ties or reinstall OEM routing clips. Leave slight slack to prevent tension on the sensor or connector.
10. 10

    Reconnect the electrical connector
    Connect the sensor electrical connector by aligning the connector halves and pushing together until a positive click is felt. If equipped with a secondary lock, slide it into place. Gently tug on the connector to verify it is fully latched.
11. 11

    Reinstall the wheel
    Place the wheel onto the hub and hand-thread all lug nuts. Tighten lug nuts in a star pattern to ensure even seating. Torque the wheel lug bolts to the Mercedes-specified value (approximately 150 Nm / 111 lb-ft — verify against W463 documentation) using a torque wrench.
    Torque spec

    Wheel Lug Nuts142.4 Nm (105 lb-ft)
12. 12

    Lower the vehicle
    Raise the vehicle slightly with the floor jack to remove the jack stands. Carefully lower the vehicle to the ground. Once the vehicle weight is fully on the wheels, perform a final torque check on the lug bolts to the Mercedes-specified value (approximately 150 Nm / 111 lb-ft — verify against W463 documentation) in a star pattern.
    Torque spec

    Wheel Lug Nuts142.4 Nm (105 lb-ft)

Reassembly

1. Installation is performed in reverse order of removal with specific torque specifications applied as noted in the procedure
2. Ensure wiring harness is routed clear of all moving suspension and steering components
3. Verify electrical connector is fully latched and secondary lock is engaged if equipped

Verification

• Start the engine and verify the ABS warning light on the instrument cluster illuminates briefly during the bulb check, then extinguishes within 3-5 seconds
• Use a Mercedes-Benz compatible scan tool (STAR Diagnostic or equivalent) to verify no active or stored ABS fault codes related to the replaced wheel speed sensor
• Perform a low-speed test drive (15-20 mph) and verify the ABS warning light does not illuminate
• With scan tool connected, monitor live data for the replaced wheel speed sensor while rotating the wheel by hand or during test drive to confirm signal is present and matches other wheel speeds during straight-line driving

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