The function of the car's rear bumper lights
The rear bumper lights of a car are mainly used to convey driving signals, assist in driving in bad weather, indicate the vehicle's outline and provide decorative reflective effects, thereby enhancing driving safety.
Signal transmission function
The rear bumper lights transmit real-time driving intentions to the rear vehicles through various lights to avoid collisions:
Brake lights: When the vehicle slows down, red lights are illuminated, warning the following vehicles to maintain a safe distance;
Turn signals: Flashing when changing lanes or turning, indicating changes in driving direction;
Reverse lights: White lights are illuminated when reversing, alerting pedestrians and following vehicles to pay attention;
Double hazard lights: High-frequency flashing when an emergency occurs, emitting a danger warning signal.
Weather assistance
Enhancing safety in conditions of low visibility such as rain, fog, and snow:
Fog lights: Have strong penetrating power, with a visible distance of up to 100 meters (far exceeding the 30-50 meters of the main lights), ensuring the following vehicles can identify the position and maintain a safe distance;
Reflective design: Reflects ambient light when there is no light source, enhancing the visibility of the vehicle outline.
Vehicle outline identification
Width indicator lights: Lit up at night or during overtaking, clearly showing the vehicle width to prevent side scratches.
When the rear bumper lights of a car malfunction, it may affect driving safety and vehicle compliance, and timely troubleshooting is required. The following are the common causes of faults and corresponding troubleshooting methods, sorted from highest to lowest priority:
1. Check if the bulb is damaged
The bulb is the most easily worn-out component of the rear bumper light. Long-term use or vibrations may cause problems such as filament melting or aging of the LED solder joints.
Inspection method: Check if the lights are completely off, off on one side, or have significantly reduced brightness.
Treatment method: Replace the new bulb that is suitable for the vehicle model. Be careful not to touch the bulb surface directly with your hands.
II. Confirm if the fuse has blown
The fuse serves as an overload protection device. If the current is abnormal, it will automatically blow, causing the entire set of lights to fail.
Inspection method: Open the fuse box inside the vehicle, look for fuses labeled "TAIL" (rear lights) or "BACK LIGHT", and check if they are broken.
Treatment method: Replace with a new fuse of the same specification (with the same amperage); if it keeps melting repeatedly, further check for circuit short-circuit issues.
III. Inspecting connection problems between lines and plugs
Frequent opening and closing of the trunk, installing or modifying accessories, or external damage may cause line damage, plug loosening or poor connection.
Typical symptoms: Flashes of lights, intermittent failure, especially when the trunk is opened, triggering the fault.
Troubleshooting methods:
Check if the wiring at the connection point between the tail light and the vehicle body is damaged or has marks of squeezing;
Use a multimeter or a test light to detect the continuity of the circuit.
Treatment method: Repair the damaged wire segment and wrap it with insulating tape, or replace the damaged wiring harness.
IV. Judging abnormality of the brake light switch or control module
If the rear bumper light is always on or off as part of the brake light, it may involve a control logic issue.
Common causes:
The brake pedal does not return to its original position, causing the switch to remain conductive;
The brake light switch is short-circuited or the contacts are stuck;
The control module sends incorrect instructions.
Treatment method:
Repeatedly step on the brake pedal 10 times to try to reset;
Replace the brake light switch (cost approximately 30–80 yuan);
Use an OBD diagnostic tool to read the fault codes and accurately locate the problem with the control module.
V. Checking the lamp cover and sealing issues
If the lamp cover is cracked or the sealing glue is aging, it will allow moisture to enter, causing short circuits, fogging inside the lamp, or corrosion.
Symptom characteristics: There are water stains inside the lamp body, oxidation marks, and the lights are dim or partially unlit.
Treatment method: Replace the new lamp cover and ensure a tight installation to prevent further water ingress.
VI. Special function misoperation troubleshooting (easily overlooked)
Some vehicles are designed with parking lights, home-coming lights, etc., which may cause the "lights are always on" illusion.
Response measures:
Confirm if the light control lever is in the "OFF" or "AUTO" mode;
Check if the steering wheel is centered, as some models will automatically illuminate the parking lights after the engine is turned off;
Reopen the driver's door or start the vehicle to reset the system.
VII. Compatibility issues with modifications (applicable to vehicles modified later)
If the rear bumper light is added later, there may be issues such as mismatched circuits with the original vehicle or conflicting control logic.
Typical phenomenon: The light should not be on but is, flashing, or triggering an instrument alarm.
Solution path:
Check if the modified components match the voltage and interface of the original vehicle;
Check if they interfere with the original vehicle's CAN bus communication;
It is recommended to have a professional electrician re-adjust the wiring or replace qualified components.
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