The core function of the daytime running lights in automobiles
In modern automotive safety configurations, daytime running lights are no longer merely decorative elements but are crucial safety features that ensure daytime driving safety. Essentially, they are signal lights rather than lighting devices, and their primary mission is to enhance the vehicle's visibility during the day, allowing pedestrians and other vehicles to detect the vehicle earlier and thereby reducing the risk of accidents.
According to authoritative data, turning on daytime running lights can reduce the accident rate of vehicles by 12.4% and the probability of fatal accidents by 26.4%. In complex lighting conditions, the role of daytime running lights is particularly prominent: on urban roads with heavy traffic, the light from the daytime running lights enables vehicles to stand out quickly among the traffic; on highways, it allows the following vehicle to detect the preceding vehicle at a greater distance, avoiding rear-end collisions; in bad weather conditions such as smog, rain, or in tunnels and shaded sections with poor visibility, the daytime running lights can significantly extend the distance at which the vehicle is recognized, leaving sufficient reaction time for other traffic participants.
In addition to safety attributes, daytime running lights also have energy-saving advantages. The power of mainstream LED daytime running lights is only 5-10 watts, which is 10%-20% of that of traditional halogen headlights. The load on the vehicle's battery is almost negligible, and even when turned on for a long time, it will not increase excessive energy consumption. At the same time, their activation and deactivation are fully automated - they are automatically lit when the engine starts and automatically turn off when the near-light is activated at night. There is no need for the driver to manually operate, which is both convenient and can avoid potential safety hazards caused by forgetting to turn them on. Nowadays, several countries including China have introduced relevant standards, requiring new passenger vehicles to be equipped with daytime running lights, demonstrating their significant importance in driving safety.
Common faults and troubleshooting methods for automotive daytime running lights
Although the structure of daytime running lights is relatively simple, they may still malfunction over time. Common problems include not lighting up, flickering, and color changes. The underlying reasons mainly lie in the following aspects:
Power supply and wiring faults
This is the most common fault cause of daytime running lights. If both sides of the daytime running lights do not light up simultaneously, the first step is to check if the fuse is blown. The fuse is usually located in the fuse box in the engine compartment or the driver's cabin, and the corresponding position can be found by referring to the vehicle manual. Replacing the fuse of the same specification can solve the problem. If only one side does not light up, it is likely a wiring issue, such as a loose plug, a wire bitten by a mouse, or a short circuit or open circuit due to aging. At this time, it is necessary to carefully inspect the wiring harness between the headlight control module and the daytime running lights, focusing on the connectors and easily worn parts, and reconnecting the loose plug or repairing the damaged wiring.
Lamp body faults
The core of LED daytime running lights is the LED chip set. Over time, they may experience chip burnout, baseboard short circuit, or poor heat dissipation leading to light attenuation. Some models of daytime running lights use an integrated design, and when faulty, the entire assembly needs to be replaced; while the split design allows for the separate replacement of the LED module. In addition, aging of the lamp cover sealing rubber strip can cause water to enter the interior, leading to a circuit short circuit and making the daytime running lights unable to work properly. This situation requires checking the sealing rubber strip and replacing it, as well as drying the internal circuit. Some owners may also encounter problems such as the daytime running lights changing color or dimming, such as the owners of NIO ES8 reporting that the headlights changed from white to yellow and the brightness decreased. This is mostly due to LED chip aging or failure of the cooling system, and requires replacement or repair of the lamps.
Control and sensor faults
Modern vehicles' daytime running lights are mostly managed by the body control module (BCM) or the lighting control unit (LCM). If the module's internal program is incorrect, the hardware is damaged, or the communication bus fails, it will cause the daytime running lights to fail to work properly. This situation requires using a professional diagnostic tool to read the fault codes to determine if the module needs repair or replacement. Additionally, the daytime running lights of some models are controlled by a light sensor. A malfunction of the sensor can cause the system to misjudge the ambient brightness, resulting in the daytime running lights not lighting up or abnormal lighting at night. At this time, it is necessary to check if the sensor is blocked or use a diagnostic tool to read the sensor data stream to confirm if its working condition is normal.
Settings and Software Issues
Some car owners have found that the daytime running lights are not lighting up, but it is actually due to an incorrect operation that they have turned off the daytime running light function. Nowadays, automotive electronic systems are complex, and some models can manually turn off the daytime running lights in the "Vehicle Settings - Lighting Settings" section of the central control screen. In such cases, simply reactivating the function is sufficient. A few models may have abnormal daytime running light functions due to an outdated software version or bugs, and this can be resolved by performing a software refresh using official diagnostic equipment.
When the daytime running lights malfunction, car owners can first check the fuses, wiring, and vehicle settings themselves. If they cannot solve the problem, it is recommended to go to a professional repair facility and use professional equipment for detection and repair to avoid unnecessary losses from blindly replacing components.
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