Why Has the Mercedes Blind Spot Assist System Stopped Working?
4 Answers
Mercedes Blind Spot Assist System stops working due to: system function failure, requiring a computer diagnosis at a 4S shop, and generally an upgrade can solve the problem. The Blind Spot Assist System relies on sensors installed at the front and rear of the vehicle to detect whether there are other vehicles approaching within a range of 3 to 15 meters around the vehicle. If there are, a red arrow will appear on the rearview mirror to alert the driver of the danger of changing lanes at this time. Taking the Mercedes E260 as an example, this car is a 4-door, 5-seat sedan with a length, width, and height of 4942mm, 1860mm, and 1455mm respectively, a wheelbase of 2939mm, a top speed of 233 kilometers per hour, a front-engine rear-wheel-drive layout, and a fuel tank capacity of 66L.
Last time my Mercedes also had the blind spot assist system go on strike, which really ticked me off. After consulting an experienced mechanic, I learned that it was most likely because the two radar sensors on the rear bumper were covered in mud or a thick layer of snow. Alternatively, the system might have been throwing a false alarm—turning the engine off and restarting it a few times could fix it. If that doesn’t work, it could be due to loose wiring connections or a blown fuse, especially since short circuits are more common in rainy weather. The worst-case scenario is a faulty sensor, which isn’t cheap to replace. If you notice the system malfunctioning while driving, be extra cautious and check your mirrors more often, and take turns and lane changes slowly. Better head to the dealership for a scan—their diagnostic tool will pinpoint the issue in no time.
My blind spot monitoring system suddenly stopped working the other day. After inspection, I found that the rear bumper sensor was covered by a car cover, which affected the signal. This issue is quite common on modified vehicles, and applying dark window films can also block radar waves. In bad weather conditions like heavy rain or fog, the radar may malfunction and automatically deactivate, but it will resume normal operation once the weather clears up. If the sensor gets knocked against the curb while parking and becomes misaligned, it may also fail. Additionally, unstable battery voltage can trigger the system's protective shutdown. If the dashboard displays a fault code after startup, remember to use the steering wheel buttons to access the engineering menu and retrieve fault details, which will help mechanics quickly identify the problem location.
As an experienced driver, I believe blind spot monitoring systems mainly fail under three circumstances: First, when the sensors are covered by dirt—remember to rinse the small square grids on both sides of the bumper during car washes. Second, when the system software malfunctions—turning off the engine for half an hour allows the module to fully power cycle and reboot. The third and most troublesome scenario is hardware damage, such as water ingress into the radar sensors or impact-induced deformation. Newer Mercedes models rely on the vehicle's network communication, so issues with the gateway module can also affect the assistance systems. During routine maintenance, don’t neglect the radar areas, and promptly clean off bird droppings or tree sap.
