How do I check my blind-spot monitoring system?

Your blind-spot monitoring (BSM) system should alert you when another vehicle is in your blind spots and may warn you during lane changes. To verify it’s working, enable the feature, inspect its sensors, and test the indicators and alerts in a safe setting. If you don’t observe or hear warnings when a vehicle is present, consult your owner’s manual or a dealership for diagnostics.

Understanding blind-spot monitoring and its indicators

Blind-spot monitoring uses radar or cameras mounted in the rear area of your vehicle to monitor adjacent lanes. When a vehicle enters your blind spot, the system typically lights an indicator in the corresponding side mirror and may emit an audible alert or message on the instrument cluster or infotainment display. Some vehicles also pair blind-spot monitoring with Cross-Traffic Alert, which warns of approaching traffic when backing up. Behavior can vary by make and model, and certain conditions (speed, weather, or sensor cleanliness) can affect performance.

Where to look and how it signals

BSM indicators are most often visible as amber icons in the side mirrors. Some cars display a warning on the instrument cluster or head-up display. Audible alerts or chimes may accompany the indicator when a vehicle is detected. Knowing where your indicators appear helps you know when the system is active and functioning.

Steps to test the system in a safe, controlled setting

To verify operation without risking safety, perform these checks in an empty parking lot or a similarly safe area with low speeds and a responsible observer. The goal is to confirm that the system detects a vehicle in the blind spot and provides a timely warning.

1. Confirm the system is enabled. Look for a BSM toggle or an option in the vehicle’s settings, and ensure the feature is turned on. Some vehicles leave BSM on by default, while others require manual activation.


2. Identify the indicator signals. While driving, notice whether the amber icon lights up in the appropriate side mirror when a vehicle approaches from your blind spot, and whether any corresponding alert appears on the instrument cluster or display.


3. Test with a second vehicle in the adjacent lane. At a safe, low speed (in a controlled area), have a parked or moving car approach from your blind spot alongside you. Signal as you would for a lane change and observe if the BSM indicator lights and/or a chime activates when the other car enters your blind spot.


4. Test Cross-Traffic Alert (if your system includes it). In a safe area, back up slowly with a helper moving laterally behind you to simulate cross-traffic. You should receive warnings if a vehicle crosses behind your path or approaches from the sides.


5. Document results and compare to conditions. Note whether warnings trigger at typical highway speeds as well as in lower-speed scenarios, and whether any warnings are delayed or absent.

In summary, you should see side-mirror indicators and hear alerts when a vehicle is detected in your blind spot, and Cross-Traffic Alert should respond when backing out in a test scenario. If nothing occurs, proceed to sensor care and professional diagnostics.

Maintenance and environmental factors that affect performance

Regular maintenance helps keep BSM effective. Environmental conditions and cleanliness directly impact sensor performance, and damage to the bumper or sensors can require recalibration or replacement.

• Clean the sensors periodically. Wipe the rear bumper sensors with water and mild soap; avoid abrasive brushes or high-pressure jets aimed directly at the sensors, which can damage them.


• Check for obstructions. Remove dirt, snow, ice, mud, or bumper decals that might cover sensors. Ensure license plates or bumper applications do not block sensor views.


• Inspect for damage. Look for cracks, misalignment, or dislodged sensors after a collision or bumper repair. Damaged sensors can reduce accuracy or cause false alerts.


• Weather and road conditions. Wet roads, heavy rain, fog, or snow can temporarily affect sensor performance. In adverse weather, rely more on mirrors and check your surroundings manually.


• Note maintenance after service. If the bumper was replaced or the vehicle underwent sensor-related repairs, the system may require recalibration at a dealership or qualified shop.

Keeping sensors clean and free of obstructions helps ensure timely warnings. If you notice frequent false alerts or a lack of warning after cleaning, the issue may require professional calibration or repair.

What to do if the system isn’t working correctly

If your BSM isn’t functioning after basic checks, follow these steps to diagnose and seek appropriate service. Remember that BSM is a supplemental safety feature and should not replace visual checking.

• Check fuses and general vehicle settings. Some models allow you to disable BSM via a fuse or menu setting; verify these are correct and that warnings are enabled.


• Review for warning messages. Some vehicles display a warning on the instrument cluster or central display if BSM or its sensors require attention or if there is a fault code.


• Inspect for physical issues. Look for damaged or misaligned sensors, bumper damage, or instances where sensors may be blocked by aftermarket components or modifications.


• Consider recalibration after maintenance. If the bumper or sensors were replaced or if the vehicle recently underwent repairs, your dealer or a qualified technician may need to recalibrate the system.


• Seek professional diagnostics. If basic checks don’t restore function, arrange a visit to a dealership or trusted auto shop for a diagnostic scan and, if needed, sensor testing and recalibration.

Persistent failure to detect vehicles or warning signs despite cleaning and checks typically requires professional inspection and calibration to ensure accuracy and safety.

Summary

Blind-spot monitoring adds a layer of awareness but is not a substitute for manual checks. Regularly ensure the feature is enabled, keep sensors clean and unobstructed, and test indicators and alerts in safe conditions. If warnings are missing or inconsistent, consult your vehicle’s manual and a professional technician to diagnose and recalibrate the system. With proper maintenance, BSM remains a helpful aid for safer lane changes and maneuvering.

What does it mean when it says check blind spot monitor system?

What Is It? Blind Spot Warning (BSW) helps you detect cars in hard-to-see areas, commonly known as “blind spots.” BSW may also be called Blind Spot Information Systems, or Blind Spot Detection. BSW systems monitor the blind spots on both sides of your car.

Why is my blind spot monitoring not working?

Your blind spot monitoring system may not be working due to dirty or blocked sensors, a system setting being turned off, or a technical issue like damaged wiring or a failed sensor. To troubleshoot, first, clean the rear bumper sensors and check your vehicle's settings menu to ensure the feature is enabled. If it's still not working, restarting the car or performing a system reset may help, but you may need professional assistance for more complex problems like wiring or sensor failure. 
This video demonstrates how to troubleshoot and reset the blind spot monitoring system: 1mDashboard warning lights YouTube · Oct 14, 2025
Common reasons and solutions

• Dirty or obstructed sensors: Snow, mud, dust, or even stickers can block the radar sensors, which are often located on the rear bumper. 
  • Solution: Clean the rear bumper, especially the corners, with water and a soft cloth. Avoid covering the sensors with any labels or stickers. 
• System settings are off: The blind spot monitoring system might have been accidentally disabled in the vehicle's dashboard menu. This can sometimes happen after a battery change. 
  • Solution: Check the vehicle's settings under a "Driving Assistance" or similar menu and turn the blind spot system back on. 
• Recent damage or repairs: A minor impact to the rear bumper can misalign or damage the sensors. 
  • Solution: Visually inspect the rear bumper for any signs of damage or recent repair work that might have interfered with the system. 
• Technical or software issues: There could be an internal wiring malfunction, a software glitch, or a failed component, such as a sensor. 
  • Solution: Try restarting the vehicle by turning it off and then on again. If that doesn't work, a system reset may help. For a persistent problem, a dealer or mechanic will need to diagnose and repair the issue, which may be covered by warranty if your car is still under one. 

This video explains how to fix a specific blind spot monitoring issue with a trailer: 51sKevin CornellYouTube · Jun 16, 2024

How do you test a blind spot sensor?

You can do this by driving the vehicle in a safe area and observing the signals from the BSM. You should also ask a friend or a helper to drive another vehicle alongside your vehicle and check if the BSM detects it and alerts you.

How to reset blind spot warning system?

To reset a blind spot warning system, first try a simple ignition cycle: turn the car off, wait 30 seconds, then start it again and drive above 10 mph. If that fails, you can disconnect the negative battery terminal for about 10 minutes to reset the control modules. For more complex issues, a calibration may be required through the vehicle's infotainment settings, or it may need to be performed with a specialized scan tool. 
Simple reset steps

• Cycle the ignition: Turn your car completely off, wait about 30 seconds, and then restart it.
• Drive the vehicle: Drive for a few minutes at speeds above 10 mph to allow the system to reinitialize.
• Disconnect the battery: If the simple reset doesn't work, disconnect the negative battery terminal for approximately 10 minutes. Then, reconnect it and try driving again. 

Calibration and advanced resets 

• Using vehicle settings: Some vehicles allow for calibration through the infotainment system or dashboard controls. Look for a "Blind Spot Monitoring" or "BSD" option in the settings menu and follow the on-screen prompts to recalibrate. 
• Using an OBD2 scanner: You can use an OBD2 scanner to check for error codes and reset the system. Plug the scanner into the port under the steering wheel and follow the scanner's instructions to clear any related codes. 
• Professional calibration: If the problem persists, the system may require a more advanced calibration. This is often performed by a dealership or a qualified mechanic using a specialized scan tool and specific calibration targets. 

When to seek professional help

• If the warning light stays on after trying the simple resets, or if the system continues to malfunction. 
• If there has been recent work done on the vehicle, especially on the rear bumper or side mirrors. 
• If the system is warning about blocked sensors, especially in severe weather, or if there is any physical damage to the sensors.