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Blind Spot Monitor (BLIS) and Cross-Traffic Alert Malfunction on 2020 Nautilus

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Mike T. · rep 0 · May 25, 4:30 AM · 1 replies · solved · Question

Vehicle: 2020 Lincoln Nautilus Reserve

My 2020 Lincoln Nautilus Reserve has been having issues with the Blind Spot Information System (BLIS) and Cross-Traffic Alert. The system often displays a 'BLIS and Cross-Traffic Alert Not Available' message on the dash, and the warning lights in the mirrors don't come on when they should.

It seems to happen more frequently after rain or a car wash, but sometimes it just pops up on a dry day. I've tried cleaning the rear bumper area where I think the sensors are, but it hasn't made a difference. Is this a common problem with the Nautilus, and what could be causing it?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 4:30 AM

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ClearTheCode admin answer: The Blind Spot Information System (BLIS) and Cross-Traffic Alert in your 2020 Lincoln Nautilus rely on radar sensors located behind the rear bumper fascia. When these systems malfunction, it typically points to an issue with these sensors, their wiring, or the control module.

Here are common causes and troubleshooting steps:

  1. Sensor Obstruction/Damage:

    • Dirt/Debris: Even if you've cleaned the surface, heavy dirt, mud, snow, or ice on the bumper fascia directly over the sensor locations can block the radar signal. Ensure the entire rear bumper is clean, especially the corners.
    • Moisture Intrusion: Water getting into the sensor housing or connectors, especially after a car wash or heavy rain, can cause temporary or permanent malfunctions. Once dried out, it might work again.
    • Physical Damage: Even a minor bump or fender bender can misalign or damage the internal components of the radar sensor, rendering it inoperable.

  2. Wiring Harness Issues: The wiring connecting the radar sensors to the vehicle's Body Control Module (BCM) or specific BLIS module can become corroded, pinched, or loose. This is more common in areas exposed to road salt and moisture.

  3. Software Glitch/Module Failure: Less common, but possible, is a software glitch requiring a module reset or update, or a complete failure of the BLIS module itself.

    • Common DTCs associated with BLIS/Cross-Traffic issues include:
      • B119F: Blind Spot Sensor Left/Right Malfunction
      • U0300: Internal Control Module Software Incompatibility

When to See a Shop:

  • If cleaning the bumper thoroughly doesn't resolve the issue.
  • If the problem persists for more than a few days after drying out.
  • If you suspect any physical damage to the rear bumper.
  • A dealership or a shop with advanced diagnostic tools can read specific BLIS DTCs, check sensor calibration, and inspect the wiring harness for continuity and corrosion. Radar sensor replacement often requires recalibration, which needs specialized equipment.
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