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2018 GLC300 Blind Spot Assist Malfunction Warning

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Diana O. · rep 0 · May 22, 4:16 AM · 1 replies · solved · Question

Vehicle: 2018 Mercedes-Benz GLC300 SUV

My 2018 Mercedes-Benz GLC300 SUV has been showing a 'Blind Spot Assist Inoperative' warning on the dash for a few weeks now. Sometimes it clears up after a restart, but it always comes back, usually within a few minutes of driving. When the warning is on, the system just doesn't work – no yellow triangle in the mirror, no audible warning.

I've checked the radar sensors in the rear bumper for any obvious damage, dirt, or obstructions, but they look perfectly fine and clean. There haven't been any recent accidents or bumper repairs either. Could this be a sensor failure, or maybe a wiring issue somewhere? It's a key safety feature, and I'd really like to get it fixed soon. Has anyone dealt with this on their GLC or other Mercedes models?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:16 AM

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ClearTheCode admin answer:

The 'Blind Spot Assist Inoperative' warning on your 2018 Mercedes-Benz GLC300 indicates an issue with the radar sensors or their associated control module and wiring. This is a critical safety feature, so addressing it promptly is important.

  1. Common Causes:

    • Radar Sensor Failure: The most frequent cause is a faulty radar sensor located behind the rear bumper. These sensors can be sensitive to impact, moisture, or simply fail over time.
    • Wiring Harness Damage: The wiring connecting the sensors to the control module can become damaged, corroded, or suffer from a poor connection. This is especially true if the vehicle has been involved in a minor rear-end collision or if water has infiltrated the bumper area.
    • Control Module Issue: The Blind Spot Assist control module itself (often integrated with other safety systems) could be faulty.
    • Sensor Misalignment/Obstruction: While you've checked for obvious obstructions, even a slight misalignment after a minor bump or improper reinstallation of the bumper can cause issues. Heavy snow or ice can also temporarily block the sensors.

  2. Diagnostic Trouble Codes (DTCs):

    • When this warning appears, the system will store specific B-codes (body electrical) or C-codes (chassis) related to the radar sensors or the Blind Spot Assist control unit. Examples might include:
      • B2204: Radar Sensor 1 Malfunction
      • B2205: Radar Sensor 2 Malfunction
      • U0100: Lost Communication with ECM/PCM (if related to a broader network issue)
    • A professional diagnostic scan tool is required to read these specific codes, which will pinpoint the exact sensor or circuit at fault.

  3. When to See a Shop:

    • Given that this is a safety system and involves complex radar technology, it's highly recommended to have your GLC300 inspected by a Mercedes-Benz dealership or a specialized independent shop.
    • They have the necessary diagnostic tools (like XENTRY/DAS) to accurately read the fault codes, test the individual sensors, check wiring integrity, and perform any required sensor calibration after replacement. Replacing a sensor often requires recalibration to ensure proper function, which cannot be done at home.
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