What kind of fault is it if the car's tail lights keep lighting up?
The continuous illumination of the car tail lights may be caused by improper operation settings, brake system failure, circuit problems, or electronic system abnormalities. Specific troubleshooting and solutions are required.
Core Fault Causes and Self-Check Methods
Improper operation or function setting issues (accounting for approximately 40%)
Lights not turned off: Check if the left knob of the steering wheel is in the "AUTO" or marker light position, and turn it to the "OFF" position and observe for 30 seconds.
Special function activation: Such as the "Escort Home" function (delayed lighting after locking the car) or accidental triggering of the parking lights by the steering wheel, turn off or correct the steering wheel through the vehicle's infotainment system.
Door/Trunk not fully closed: Press all the doors and trunks forcefully to confirm that there is no unopened prompt on the dashboard (some models may trigger warning lights).
Brake system failure (accounting for approximately 35%)
Brake light switch damage: Test the rebound of the brake pedal to see if it is smooth. If it is stuck or the tail lights are constantly on, replace the switch.
Insufficient brake fluid or handbrake not released: Check the brake fluid level (between MIN-MAX) and completely release the handbrake and check the sensor.
Brake pad wear: Replace when the thickness is less than 3mm; otherwise, it may trigger an abnormal signal.
Circuit and hardware faults (accounting for approximately 25%)
Short circuit or fuse melting in the wiring: Check if the insulation layer of the tail light wiring is damaged and use a multimeter to test the continuity (do not operate by non-professionals).
Light bulb or control module malfunction: Remove the lamp cover to observe if the light bulb is black (indicating a short circuit sign), or disconnect the negative battery terminal for 15 minutes to reset the BCM module.
Emergency Handling and Maintenance Suggestions
Immediate Actions:
If accompanied by dashboard fault lights (such as ABS warning), pull over to the side of the road and call for help.
Temporary removal of the emergency power plug from the trunk to prevent battery depletion (wrap the contact points with insulating tape).
Maintenance Priority:
Self-repair: Replace the light bulb, reset the switch, or replenish the brake fluid (DOT4 standard).
Repair scenarios: Short circuit in the wiring, BCM module failure (diagnostic code reading), or brake system hardware damage.
Whether to replace the tail light assembly
Judgment criteria for whether to replace:
Minor damage: Try local repair or replace only the lamp cover
Situation: The surface of the lamp cover has only 1-2 centimeters of shallow cracks, not penetrating the inner layer sealant, and not damaging the internal LED lamp beads or reflector structure.
Handling method: Professional technicians can use automotive-specific acrylic glue for repair. After repair, conduct a 24-hour waterproof test (spraying water to observe if there is fog inside) to ensure sealing.
Note: If the tail light housing is not an integrated design and the lamp cover can be removed, you can purchase original or aftermarket separate lamp covers for replacement, with a price of approximately 1/3 to 1/2 of the total assembly.
Severe damage: Must replace the entire tail light assembly
Situation: Any of the following conditions must be replaced, not just repair or replace the lamp cover:
Large area cracking: The damaged area exceeds 1/3 of the lamp cover's total area.
Seal layer damage: Cracks have penetrated the inner layer sealant, causing water infiltration, water accumulation, or persistent water mist.
Structural damage: The connection clips between the lamp housing and the vehicle body break, or the entire lamp housing deforms, causing a deviation in the light beam direction.
Affecting function: The brake light or marker light area is damaged, causing the light brightness to decrease by more than 30%. Reason: These situations will seriously damage the waterproof and sealing properties of the tail lights, causing internal circuit corrosion, short circuits, and even triggering serious safety hazards such as constantly illuminated brake lights, which violate the requirements of "Technical Conditions for Motor Vehicle Operation Safety" (GB7258-2017).
Tail light structure is crucial
Non-integrated tail lights: The lamp cover can be detached and is a prerequisite for local repair or replacement of the lamp cover.
Integrated tail lights: The lamp cover is designed as a single unit with the internal structure, and cannot be replaced individually. Once the shell is damaged, the entire tail light assembly must be replaced.
Safety is the bottom line
Regardless of the size of the damage, it should be dealt with as soon as possible. Even minor damage may allow rain and dust to enter the interior, causing long-term erosion of the circuit, shortening the lifespan of the bulb, and ultimately leading to more expensive malfunctions.
Recommendation: If one cannot determine the degree of damage or the structure of the tail light by themselves, the safest approach is to go to a 4S store or a professional automotive repair shop and have an experienced technician conduct an inspection and assessment to ensure driving safety and make the most economical decision.
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