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2020 ES 300h Blind Spot Monitor Malfunction Warning

0

Mike T. · rep 0 · May 25, 3:28 AM · 1 replies · solved · Question

Vehicle: 2020 Lexus ES 300h Luxury

My 2020 Lexus ES 300h Luxury trim recently started showing a "Blind Spot Monitor Malfunction" warning on the dash. The BSM system just isn't working anymore, and the little indicators in the side mirrors don't light up.

I haven't had any accidents or bumps, and the sensors in the rear bumper look clean and unobstructed. I tried restarting the car a few times, but the warning always comes back.

Is this a common issue with these models? What could be causing it? Any simple fixes I can try before heading to the dealership?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:28 AM

0

ClearTheCode admin answer:

  1. Check Sensor Areas: Even if they look clean, ensure the rear bumper areas where the BSM sensors are located (usually behind the corners of the bumper cover) are absolutely free of dirt, mud, ice, or any obstruction. Sometimes a thin layer of grime can be enough.
  2. Toggle BSM On/Off: Locate the BSM button (often near the steering wheel or on the dash) and try toggling the system off and on a few times. This can sometimes reset a minor glitch.
  3. Battery Disconnect: A temporary fix for many electrical glitches can be to disconnect the negative terminal of your car battery for 15-20 minutes, then reconnect it. This can reset various modules, but be aware it might also reset radio presets and other settings.
  4. OBD Scan: A diagnostic scan tool can pull specific codes related to the BSM system. Common codes include B1580 (Blind Spot Monitor System Malfunction) or U0155 (Lost Communication With Instrument Panel Cluster Control Module), which might point to a communication issue.

Common Causes:

  • Blocked Sensors: The most common cause is an obstruction to the radar sensors in the rear bumper.
  • Wiring Damage: Damage to the wiring harness leading to the BSM sensors or module, perhaps from road debris or a minor impact not visible externally.
  • Faulty Sensor/Module: One of the radar sensors or the main BSM control module itself could be faulty.
  • Software Glitch: Less common, but sometimes a software issue in the vehicle's computer system can cause these warnings.

When to See a Shop: If cleaning and toggling don't resolve the issue, or if you pull a specific B-code or U-code, it's time to visit a Lexus dealership or a specialist shop. BSM systems are complex and require specialized diagnostic tools to pinpoint the exact component failure and recalibrate if a sensor or module is replaced. Driving with a malfunctioning BSM isn't critical for safety but disables a useful driver assist feature.

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