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Blind Spot Monitor (BSM) System Fault on 2021 CT5

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Mike T. · rep 0 · May 25, 2:53 AM · 1 replies · solved · Question

Vehicle: 2021 Cadillac CT5 Sport

My 2021 Cadillac CT5 Sport is displaying a persistent "Service Blind Spot Monitoring System" message on the dashboard, and the indicators in the side mirrors for both the BSM and Rear Cross-Traffic Alert (RCTA) systems are no longer working. It started intermittently a few weeks ago, but now it seems to be a constant issue.

I've visually checked the sensors located in the rear bumper for any obvious obstructions, dirt, or damage, but everything appears clear and intact. Is this a common problem with the 2021 CT5, and what's usually the underlying cause? Could it be a sensor, wiring, or a module issue?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:53 AM

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ClearTheCode admin answer:

Blind Spot Monitoring (BSM) and Rear Cross-Traffic Alert (RCTA) systems are critical safety features, and a "Service" message indicates a fault in the electrical or sensor components.

  1. Sensor Obstruction/Damage: While you've checked, even minor dirt, ice, or a subtle bumper misalignment can affect the radar sensors. A previous minor fender bender, even if repaired, could have knocked a sensor out of alignment. The sensors are typically located behind the rear bumper cover.
  2. Wiring Issues: The wiring harness connecting the radar sensors to the main vehicle network (CAN bus) can be susceptible to damage, corrosion, or loose connections. This is especially true in areas exposed to road debris and weather.
  3. Sensor Failure: The radar sensors themselves can fail internally. They are complex electronic components that can degrade over time or due to impacts.
  4. Rear Bumper Module (RBM) / Object Detection Module Failure: The BSM/RCTA system relies on a dedicated control module, often located in the rear of the vehicle, to process the sensor data. A fault in this module can cause the entire system to malfunction. Diagnostic trouble codes (DTCs) can often pinpoint this.
    • Common DTCs: You might see codes like U0232 (Lost Communication with Rear Object Detection Control Module) or codes specific to individual sensor performance (e.g., related to radar signal range or plausibility).
  5. Software Glitch/Recalibration: Sometimes, a software glitch or a need for recalibration after a battery disconnect or minor impact can cause these errors. Dealerships have specific tools for sensor recalibration.

When to See a Shop: Given that the issue is persistent and affects a safety system, it's crucial to have your CT5 inspected by a Cadillac dealership or a specialist in advanced driver-assistance systems (ADAS). They have the necessary diagnostic equipment to:

  • Read specific BSM/RCTA system fault codes.
  • Test the individual radar sensors.
  • Check the wiring integrity.
  • Determine if the control module is faulty.
  • Perform any necessary sensor recalibrations or software updates. Driving with a malfunctioning BSM/RCTA system compromises your vehicle's safety features.
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