WARNING: This page does not describe the selected car, but rather 26 other vehicles, including the 1999 Mercedes-Benz SLK230, 1999 Mercedes-Benz ML430, 1999 Mercedes-Benz ML320, 1999 Mercedes-Benz E430, and 1999 Mercedes-Benz E320. However, it is still accessible from the selected car via links, so may be relevant.

Rod-shaped speed sensors (impulse transmitters) measure wheel speeds. Three speed sensors measure wheel speed of each front wheel and both rear wheels. Speed sensors for front axle are on steering knuckles. Speed sensor for rear axle is on axle housing. Drive pinion serves to measure rear wheel speed.

Speed sensor measures wheel speed by sensing rotor teeth movement. On front axle, rotor teeth are machined into front wheel hub. See Fig 1.

On rear axle, toothed rotor is pressed on drive pinion. Axles with different ratios have gear wheels with different number of teeth. Speed sensors consist of magnetic core and coil. Rotation of rotor, set specific distance from sensor, causes alternating voltage in coil.

Fig 1: Cutaway View Of ABS Speed Sensor

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

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.

Safety Warning

Speed Sensor

Use the Manual With the Right Hardware

When to See a Mechanic