What kind of fault is it if the car's tail lights keep lighting up?
The most common reasons for the tail lights to remain on constantly are brake light switch failure, the light switch not being reset, or wiring problems. First, check if there was any accidental operation, and then investigate hardware faults.
What could be the issue? The most common cases are:
- Brake light switch failure: The switch on the pedal is stuck or the adhesive pin is broken, and the brake light keeps on when the brake is released. This is the most common reason.
- The light switch is not turned off: The knob is not rotated back to the OFF position after parking, or the automatic headlights function is activated.
- Wiring short circuit/grounding: The wire is damaged and the positive and negative poles are in contact, causing the tail lights to remain on uncontrollably.
What else could be possible?
- Parking light function: In some models, one of the rear lights will be on for a while after locking the car, which is a normal design.
- The "Let Me Home" function: The tail lights will automatically light up for a while after the engine is turned off. This function can be disabled.
- Control module failure: The BCM module sends an incorrect signal abnormally, which is less common but has high repair costs.
- The car door is not closed properly: This causes the vehicle not to enter a fully dormant state.
How to handle it?
First, check the position of the light switch and whether the car door is closed properly.
Temporarily, you can use a piece of tissue paper or a balancing block to press the brake pedal switch to deal with it temporarily.
If the lights remain constantly on, it will deplete the battery. It is recommended to go to a repair shop as soon as possible to test and replace the switch or check the wiring.
The core function of the car's tail lights is to identify the presence and outline of the vehicle in the night or low visibility conditions, and convey the driving status (such as braking, steering, reversing) to the rear to prevent rear-end collisions and ensure driving safety.
Main functional components and their functions:
- Position lights (width lights): Turned on at night, red and constantly on, indicating the width and position of the vehicle, allowing the following vehicle to determine the outline of the preceding vehicle.
- Brake lights (brake indicator lights): Bright red flashes or constantly on when braking, forcing a warning to the following vehicle that "it is slowing down/停车ing".
- Turn signal lights： Yellow/orange flashing， indicating that the vehicle is about to change lanes or turn to the left or right.
- Reverse lights： White constantly on， automatically illuminated when in reverse gear， serving both to illuminate the rear road and to warn the following vehicle that the vehicle is reversing.
- High-position brake lights： Installed on the rear window， higher and more conspicuous， supplementing the traditional brake lights to reduce the risk of being blocked by large vehicles.
- Rear reflectors： Passive device， reflecting the light of the following vehicle， allowing the vehicle to be identified even when the power is off at night.
Key precautions：
- Strict color standards： Red (width/brake/mist lights)， yellow (turning)， white (reverse). Mixing or incorrect installation is illegal and dangerous.
- Special phenomena of electric vehicles： In some electric vehicles， the brake lights may not light up during low-intensity kinetic energy recovery deceleration. The new national standard (GB 21670—2025) has stipulated that when the deceleration is greater than 1.3m/s²， the brake lights must be illuminated.
- Risk of design trend： If the continuous and pixelated tail lights overly pursue aesthetics and result in a decrease in signal recognition (such as insufficiently bright brake lights or too small turn signal lights)， it will increase the delay in the judgment by the following vehicle， and it must comply with safety standards.
Regularly check if the tail lights are in good condition (especially the brake lights and turn signal lights). If damaged， it should be repaired promptly to ensure clear and effective light signals.
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