ABS Light Stuck On in Your Mercedes GLS X167? Start Here

Seeing the ABS warning light stay on in your Mercedes-Benz GLS X167 is unsettling, but it's rarely a sign of imminent brake failure. In most cases, the light means the anti-lock braking system has disabled itself because it detected a fault—often from a wheel speed sensor or its wiring. The good news is that many of these faults are straightforward to diagnose with the right scan tool, and the fix is frequently a single sensor rather than a major assembly. That said, it's important to confirm the exact cause before replacing parts, because the X167's ABS/ESP system also relies on wheel speed data for traction control, stability control, and hill assist.

Likely causes and what to check first

Before diving in, pull the fault codes with a Mercedes-specific scanner (Xentry or a capable aftermarket tool). Generic OBD-II readers often can't read ABS codes on these vehicles, so a proper scan is your first step—it will usually tell you which wheel is affected and whether the issue is electrical or mechanical. From there, here's what to inspect, roughly in order of likelihood:

• Wheel speed sensor – The most common culprit. On most X167s, each sensor is a separate part that unbolts from the hub or steering knuckle. Look for a damaged sensor tip, corrosion, or debris (metal shavings can stick to the magnetic tip).
• Wiring and connector – The sensor's harness runs near the wheel well and can chafe, crack, or corrode. Check for broken wires, pushed pins, or water intrusion in the connector. A wiggle test while watching live data can reveal an intermittent fault.
• Tone ring / magnetic encoder – This is the toothed or magnetic ring the sensor reads. On some Mercedes models, it's integrated into the wheel bearing or hub; on others, it's a separate ring. If the ring is damaged or heavily contaminated, the sensor may need to be replaced along with it—or, depending on the design, the hub/bearing assembly. Confirm the setup for your exact model year and axle before ordering parts.
• ABS control module – Less common, but possible. Symptoms can include multiple wheel speed codes or communication faults. On many X167s, the module can be repaired or replaced separately, though it may need coding afterward. Don't jump to this until the simpler items are ruled out.
• Battery / charging voltage – A weak battery or failing alternator can cause a cascade of warning lights, including ABS. If you see other electrical gremlins, check system voltage first.

Is it safe to keep driving?

If the only light on is the amber ABS warning and your brakes feel normal, you can usually drive cautiously to a workshop for diagnosis. Remember that ABS is disabled, so the wheels can lock under hard braking—especially on wet, icy, or loose surfaces. Traction control and stability control may also be reduced or off. Avoid emergency stops and slippery roads, and don't delay the repair. If you also see a red brake warning light, the brake pedal feels soft or goes to the floor, or you hear grinding noises, stop driving and have the vehicle towed. Those signs point to a hydraulic or mechanical brake issue, not just a sensor.

Repair approach and final thoughts

In most cases, a wheel speed sensor fault is resolved by replacing the affected sensor and clearing the codes. If the tone ring is damaged, you may need that ring or, on some axles, the hub/bearing assembly—but that's a fallback, not the default. The same goes for the ABS module: repair or replacement is sometimes necessary, but only after wiring and sensors are proven good. Because Mercedes changed sensor and hub designs across model years and trims, it's best to confirm the exact part number and procedure for your GLS X167's VIN. A proper diagnosis with live wheel speed data will save you from guessing and ensure the fix actually turns the light off.

This material is AI-generated and for informational purposes only — it does not replace an in-person diagnosis by a qualified mechanic.