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BSM stands for blind-spot monitoring, a term for systems that survey and monitor locations adjacent to and behind vehicles. This assists in driving by detecting vehicles outside of the driver’s and side mirrors’ view.

Different manufacturers have different names for their BMS systems. For example, Audi has Audi Side Assist while Ford has its Blind Spot Information System (BLIS). While they have different names, their features and functionality are pretty similar.

How Does a BSM System Work?

BSM is a system that utilizes cameras and radars to detect vehicles in the driver’s blind spot. Some vehicles have radar sensors placed on the mirrors or rear of the vehicle, while others use cameras near the side mirrors.

When the system detects a vehicle approaching from the blind spot, it activates a warning light on the outside mirror or roof pillar on the side of the incoming vehicle. The signal differs depending on the manufacturer. Generally, you can expect a flashing light or an audio warning.

Other BSM systems pair with the rear cross-traffic alert system. This system uses sensors that detect oncoming vehicles and pedestrians when the car is in reverse. Similarly, it alerts the passengers using a visual or audible signal.

You have the option to separate the two systems or add one or the other, depending on the vehicle model.

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Additionally, the BSM system works with lane keep assists to apply the brakes when the turn signal is activated if there’s an oncoming vehicle in the next lane or approaching behind.

Types of BSM Systems

There are two types of BSM: blind-spot warning systems and automatic emergency steering systems.

Blind-Spot Warning

This system is the most common one, as it visually and/or audibly alerts the driver of any oncoming vehicles or objects in the blind spot.

Additionally, a more complex version of this system has an audible warning that alerts the driver if there is a vehicle/object in the lane you’re merging into while the turn signal is on.

Automatic Emergency Steering

As the name suggests, this BSM system engages the brakes and steers you back to your lane if you attempt to drive into a blind spot occupied by a vehicle. In addition, it also gives visual and/or audible warnings for any oncoming cars.

Why Is the BSM Light On?

The BSM light automatically illuminates when the system is on and there’s an approaching vehicle detected in a blind spot. However, if you’re sure there aren’t any oncoming cars or pedestrians, then it might be due to a false alarm.

Nonetheless, there are different reasons why your BSM light is on. Here are some of the common ones:

Objects in the Blind Spot

The BSM system is designed to detect vehicles and notify the driver. As such, there are cases when a pedestrian or any other object gets mistaken for a car. The false alarm frequently happens in parking lots where shopping carts and the likes are frequent.

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Similarly, the system also can mistake parked cars for moving ones.

Malfunctioning System

The incorrectly detected object malfunction happens quite often, but there are also cases where the system is malfunctioning altogether. When this happens, the BSM light comes on and continuously blinks.

It’s often due to a damaged sensor, wiring issues, or any other faulty components. It’s recommended to take your vehicle to a mechanic or to the vehicle’s manufacturer when this happens. They can repair such issues, but replacing the components or the system itself could be the better course of action.

Blocked Sensors

You can also pin the issue on blocked sensors. Since the radars or cameras are located on the rear bumper, debris could block them. This prevents the BSM system from working properly, as it could detect the obstruction as a moving object.

Luckily, you can clean the sensors yourself by wiping away the dirt obstructing their vision.

Low Battery Power

The BSM system relies on the car’s battery for power. Low battery power could lead to the system not functioning altogether, or the light continuously blinking. In such cases, it’s advisable to replace the battery if needed.

Software Update

The BSM light may illuminate during much-needed software updates. Don’t fret, most systems roll out updates automatically and will function as intended as soon as they’re done.

Advantages of the BSM System

Using the BSM system is a safety precaution that benefits the driver. Here are some scenarios where its advantages stand out:

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Reduces Parking Accidents

Public parking lots are littered with cars going in and out of the vicinity. Due to this, the BSM system is a great way to navigate tight corners without the worry of hitting another car.

Enhanced Awareness

Driving on a highway can be tricky due to how unpredictable some drivers are. With the BSM system, you’ll have enhanced awareness of any oncoming cars because of the constant alerts and notifications.

Easier to Change Lanes

Entering the fast lane is dangerous because of speeding cars, turning the system on will alert you of any oncoming vehicles, making it easier to switch lanes.

How Do I Turn On/Off the BSM?

Press the BSM button located on the dashboard to turn the system on or off.

Final Thoughts

The BSM button on your vehicle’s dashboard stands for blind-spot monitoring. It’s a system that helps detect any oncoming cars or pedestrians from the driver’s blind spot. The system is one of the many new car technologies that aim to make driving easier.

The BSM light turns on when the system detects movement, so it’s susceptible to false alarms. Objects in the blind spot, a malfunctioning electrical component, low battery power, and blocked sensors are some of the few causes of false alarms.

About The Author
CarParts Research Team
Written By Research Team

Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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