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2019 NX 300 Blind Spot Monitor (BSM) Warning Intermittent

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Mike T. · rep 0 · May 25, 3:24 AM · 1 replies · solved · Question

Vehicle: 2019 Lexus NX 300 Base

Hello Lexus owners, I'm having an intermittent issue with the Blind Spot Monitor (BSM) system on my 2019 Lexus NX 300 (Base trim). Sometimes when I start the car, I get a 'BSM System Malfunction' warning on the dash, and the system just doesn't work.

Other times, it works perfectly fine for days. There doesn't seem to be any pattern – not related to weather, dirt, or anything I can pinpoint. I've checked the sensors in the rear bumper for obstructions, and they look clean. Has anyone else experienced this kind of intermittent BSM warning? What could be causing it to act up like this?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:24 AM

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ClearTheCode admin answer: Intermittent Blind Spot Monitor (BSM) warnings on your 2019 Lexus NX 300 can be frustrating because they are difficult to reproduce consistently. The BSM system relies on radar sensors, wiring, and the vehicle's ECU to function correctly.

Here are the common causes and steps to diagnose:

  1. Sensor Obstruction/Damage: While you've checked for dirt, even minor damage to the bumper cover where the sensors are located, or a slight misalignment, can affect their operation. Sometimes, heavy rain or snow can temporarily interfere, but you mentioned it's not weather-related.
  2. Wiring Issues: Intermittent electrical problems are often traced back to loose, corroded, or damaged wiring and connectors. A faulty connection to one of the radar sensors or the BSM control module could be causing the system to cut out sporadically.
  3. Software Glitch: Sometimes, a software anomaly or a temporary communication error within the vehicle's network can trigger these warnings. A simple battery reset (disconnecting the 12V battery for 15-20 minutes) can sometimes resolve minor software glitches, but this should be done carefully to avoid losing other settings.
  4. Faulty BSM Sensor: One of the radar sensors themselves could be failing intermittently. As electronic components age, they can sometimes work fine until a specific temperature or vibration causes an internal fault.
  5. BSM Control Module: Less commonly, the BSM control module itself could be faulty, leading to inconsistent operation.

When to see a shop:

  • Diagnostic Scan: Even without a persistent warning, a Lexus dealership or a shop with advanced diagnostic tools can often pull 'history codes' or 'pending codes' related to the BSM system. These codes can point directly to the sensor or circuit that's acting up.
  • Professional Inspection: A technician can visually inspect the wiring harnesses and connectors for the BSM sensors, check for any physical damage to the sensors, and perform calibration checks if necessary.
  • Persistent Issue: If the problem continues to occur, especially if it starts happening more frequently, it's essential to have it professionally diagnosed to ensure the safety feature is reliable.
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