The function of the car's rear lights
The rear lights of a car are a combined signaling and lighting system installed at the rear of the vehicle. Their main function is to convey the driving status, warn of danger, and provide rearward illumination, aiming to prevent rear-end collisions and ensure driving safety.
Core Function Classification
Width indicator lights (rear position lights): They emit a constant red light at night or in low visibility conditions, indicating the presence of the vehicle and its width, preventing the rear vehicle from misjudging the distance.
Brake lights (emergency brake lights): They emit a high-intensity red light when the brake is applied (including high-position brake lights), serving as a mandatory warning to the rear vehicle to slow down or stop, a key device to prevent rear-end collisions.
Turn signal lights: They emit a flashing yellow/orange light, informing the vehicles behind of the intention to change lanes or turn.
Reverse lights: When in reverse gear, they automatically illuminate with a white light, illuminating the rear road surface and warning pedestrians and the rear vehicle "reversing in progress".
Rear fog lights: In bad weather conditions (fog, rain, snow), they turn on high-penetration red lights, significantly enhancing the visibility of the vehicle in low-visibility environments (not for daily use).
Key Features
Linkage Mechanism: Each light is automatically controlled by the pedal, gear, or switch (such as the reverse lights turning on/off with the gear position, and the brake lights turning on/off with the pedal). They cannot be manually turned off.
Color Specification: Red (width indicator/brake/rear fog), Yellow (turning), White (reverse), color confusion is considered a violation or fault.
Integrated Form: Modern vehicles often adopt a combined rear light design, integrating the above functions into the same light assembly. Some models may feature a continuous design or LED/OLED light sources.
The core failure of car rear lights is manifested as failure to light up, constant illumination, or abnormal flashing. The main causes are usually lamp bulb burnout, fuse melting, poor contact, or faults in the wiring or switch. The troubleshooting should be carried out in the order of "from easy to difficult".
Common Fault Phenomena and Corresponding Main Causes
Single-side failure to light up: It is likely to be a burned-out lamp bulb or poor contact of the lamp socket (the probability of both sides failing simultaneously is extremely low).
Both sides fail to light up: The priority check should be on the shared fuse melting, failure of the lighting switch, or breakage of the main circuit.
After engine shutdown, the lights remain on: It is mostly due to stuck or jammed brake pedal switch, incorrect activation of the parking lights, or short circuit in the control module, which can easily lead to battery depletion.
LED tail lights fail to light up: It is not a filament issue; it is usually due to damage of the driving module or detachment of the welding points, and requires replacement of the entire module.
Self-checking Steps (Operate in sequence)
Check the lamp bulb: Open the trunk, remove the lamp cover, and observe if the filament is broken or the glass is blackened; if it is an LED source, visually check for obvious damage. Check for single-side failure to light up first.
Check the fuse: Consult the manual to find the location of the fuse for the rear lights (usually under the dashboard or in the engine compartment). If the metal wire is broken, replace it with a new one of the same specification.
Check connections and grounding: Check if the lamp socket plug is loose, corroded, and tightened; check if the grounding wire is secure.
Test the switch function: Step on the brake pedal to observe the reaction of the brake lights. If they are completely non-functional and the lamp bulb is normal, it may be a fault in the brake light switch; check if the lighting control lever has mistakenly triggered the parking light mode.
Professional Diagnosis: If all the above are normal but still faulty, it may involve faults in the circuit shorting/rupture or the body control module. Use a multimeter or OBD diagnostic tool for testing. It is recommended to send it for repair. Notes for Attention
Do not mix different bulb specifications: When replacing, strictly match the original wattage and model. Otherwise, it may burn out the circuit or cause abnormal brightness.
Safety first: When checking the wiring or involving brake system components, if you do not have an electrical engineering background, please go directly to the repair shop to avoid short circuits or brake failure risks.
Speciality of LED models: For some new car rear lights, the integration is high and the bulb cannot be replaced separately. The entire assembly or driver board needs to be replaced.
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