ABS & ESP Warning Lights On - 2018 GLC300

ClearTheCode admin answer:

When both the ABS (Anti-lock Braking System) and ESP (Electronic Stability Program) warning lights illuminate simultaneously on your 2018 Mercedes-Benz GLC300, it indicates a fault within the vehicle's braking and stability control systems. These systems are interconnected, so a fault in one often triggers a warning for the other.

Common Causes & Diagnostics:

1. Wheel Speed Sensors: This is the most common cause. Each wheel has a sensor that monitors its rotational speed. If a sensor fails, becomes dirty, or its wiring is damaged, the ABS/ESP control unit loses crucial data, triggering the warning lights. Common OBD-II codes include C0031, C0032, C0033, C0034, C0035 (indicating a fault with a specific wheel speed sensor).
2. ABS Control Module Failure: Less common but more serious, the ABS control module itself can fail. This module processes data from the wheel speed sensors and controls the ABS/ESP functions. A faulty module can lead to various warning lights and system malfunctions. Codes like C0020 (ABS Pump Motor Control) or internal module fault codes might appear.
3. Brake Light Switch: A faulty brake light switch can sometimes cause these lights to come on, as the ABS/ESP system relies on accurate brake pedal input. This is a relatively inexpensive fix.
4. Steering Angle Sensor: The ESP system uses the steering angle sensor to determine the driver's intended direction. If this sensor is faulty or out of calibration, it can trigger the ESP light, and often the ABS light as well. Codes like C1172 (Steering Angle Sensor Fault) are possible.
5. Low Brake Fluid Level: While usually indicated by a separate brake warning light, extremely low brake fluid can sometimes affect the pressure sensors and trigger ABS/ESP warnings.

When to See a Shop:

While your braking performance might seem normal for now, the ABS and ESP systems are crucial for preventing wheel lock-up during hard braking and maintaining vehicle stability during skids. Driving with these lights on means these safety features are disabled. It's highly recommended to have your GLC300 scanned and diagnosed by a professional mechanic as soon as possible. They can read the specific fault codes, which will pinpoint the exact issue and allow for an accurate repair, restoring your vehicle's full safety capabilities.