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2019 CLA250 ABS/ESP Warning Lights On - Wheel Speed Sensor?

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Mike T. · rep 0 · May 25, 3:04 AM · 1 replies · solved · Question

Vehicle: 2019 Mercedes-Benz CLA250 C117

Hello ClearTheCode community,

My 2019 Mercedes-Benz CLA250 (C117) recently had its ABS and ESP warning lights illuminate on the dashboard. They came on simultaneously and have stayed on. I haven't noticed any immediate driving issues, but I know these systems are crucial for safety.

I'm guessing it might be a wheel speed sensor, as that seems to be a common cause for these lights on many cars. Is this a frequent problem on the CLA250? How can I confirm which sensor it might be without taking it straight to the dealer?

I'd appreciate any guidance on diagnosing this issue. I'm hoping it's a relatively straightforward fix.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:04 AM

0

ClearTheCode admin answer:

When both the ABS (Anti-lock Braking System) and ESP (Electronic Stability Program) warning lights illuminate on your 2019 Mercedes-Benz CLA250, it strongly suggests an issue with a shared component or system that impacts both. Your suspicion about a wheel speed sensor is very likely correct, as these sensors are critical inputs for both systems.

Here's a breakdown of common causes and diagnostic approaches:

  1. Common Causes for ABS/ESP Lights:

    • Faulty Wheel Speed Sensor: This is the most frequent cause. Each wheel has a sensor that monitors its rotational speed. If one fails, the ABS/ESP system loses crucial data.
    • Damaged Wheel Speed Sensor Wiring: The wiring to the sensors can get damaged by road debris, corrosion, or during other service work.
    • Faulty ABS Control Module: Less common, but the module itself can fail.
    • Tone Ring/ABS Ring Damage: The toothed ring that the sensor reads can become damaged or clogged with debris, leading to incorrect readings.
    • Low Brake Fluid: While less common for simultaneous ABS/ESP lights, low fluid can sometimes trigger warnings, especially if combined with other issues.

  2. Diagnostic Steps You Can Take:

    • Scan for Codes: While you don't have a Check Engine Light, you will almost certainly have stored codes in the ABS/ESP module. A standard OBD-II scanner might not access these, but a more advanced scanner (like an iCarsoft MB II or similar Mercedes-specific tool) will. Look for codes like C0031 (Left Front Wheel Speed Sensor), C0034 (Right Front), C0037 (Left Rear), C003A (Right Rear), etc. This will pinpoint the exact sensor.
    • Visual Inspection: Once you know which wheel is affected, visually inspect the wheel speed sensor and its wiring at that wheel. Look for any signs of physical damage, corrosion, or loose connections. Also, check the tone ring (often visible behind the brake rotor, or integrated into the wheel bearing) for damage or excessive dirt.
    • Check Brake Fluid Level: Ensure your brake fluid reservoir is filled to the appropriate level.

  3. When to See a Shop:

    • If you can't access the ABS/ESP specific codes with your scanner, or if your visual inspection doesn't reveal an obvious issue, it's best to take your CLA250 to a Mercedes-Benz specialist.
    • They have the proprietary diagnostic tools (like XENTRY/DAS) that can read all fault codes, perform live data monitoring of each wheel speed sensor, and accurately diagnose the root cause.
    • While replacing a wheel speed sensor can be a DIY job for some, ensuring the correct part is installed and that the system is functioning properly afterwards is important for your safety. An incorrect diagnosis could lead to replacing the wrong part or missing a more serious issue.
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