Rear Light Failure Warning Light (Solved & Explained)

When there is an issue with the rear light system, the dashboard will light up with the rear light failure warning and alert the driver. There are several reasons why this light turns on, as there could be a problem with the sensor, electricity, bulb, or level of humidity around the bulb.

Why Does The Rear Light Failure Warning Light Turn on?

The main reason why the rear light failure warning light turns on is that the sensors around the rear lights can detect if there is an issue developing around the lights.

The warning light does not just turn on only when the bulb is about to go out. There are several different reasons why the rear light warning light will turn on and not all of the reasons can be seen with the human eye. 

If you cannot find the reason why the rear light failure warning light is on, then you will have to go to a mechanic.

The mechanic can use their diagnostic tools and retrieve information from your vehicle’s diagnostic system. Then the mechanic will be able to use the information that the sensors have detected to diagnose the problem. 

What Do Sensors Have to Do With the Rear Light System?

It is the sensors that provide information to the diagnostic system within a vehicle. If there’s an issue with the sensor, then the sensors will not be able to provide accurate information.

There are sensors all around a vehicle. There are gas sensors, engine sensors, hydraulic combustion sensors, electrical sensors, Center is attached to the steering and suspension, and there are sensors for the lighting system.

The front light and the brake lights and tail-lights all have their own sensors. If a vehicle does not have sensors, it would be much more difficult to diagnose vehicular problems.

As stated above, the rear light failure warning light will turn on even if there is an issue with the sensor. It does not only turn on when there is an issue with the electricity or the bulbs. Having accurate sensors is critical to the performance of a vehicle. 

Reasons Why The Rear Light Failure Light Turns On:

There are a myriad of reasons why the rear light failure light would turn on. The best way to determine where the issue is in the rear light system is to purchase a diagnostic tool and use it on your vehicle. You can also take your vehicle to a mechanic.

  • The rear light bulbs are about to go out. 
  • There is an issue with the electricity flowing to the rear light system
  • The bulb is loose
  • There is far too much humidity trapped inside of the rear brake light and it is affecting the electrical system
  • There’s an issue with the sensor and it cannot provide accurate information about the rear brake system
  • The rear light failure warning system itself is malfunctioning and needs to be taken in to get serviced and repaired

If there is no light coming from one or both of your rear lights, then you may be pulled over by a cop. The rear light on the back of every vehicle is supposed to let other drivers know about your presence in the darkness of the night.

If your rear lights do not work, then vehicles behind you will not know that you are there. They could crash into you.

How to Fix Rear Light Issues

The following solutions can help fix any issues that you may be experiencing due to the rear light warning lights. Some of these solutions can be performed by the average car owner and other issues may require a mechanic’s help.

The rear light bulb is about to go out

The average life expectancy of a rear light bulb is about five or six years. Sensors will be able to detect when the bulb is no longer working at its optimum level.

The sensors then will indicate to the car’s main diagnostic center that the bulbs need to be replaced. The diagnostic system will turn on the rear light warning light. You can fix the issue by replacing the bulbs.

There’s an issue with electricity flowing to the rear light system.

The most common electrical issue in a vehicle is aging parts and parts that were not properly installed. There could also be an issue with faulty wiring or a blown-out fuse.

A mechanic’s diagnosing tools can determine the cause of the faulty wiring. Then they can fix the electrical issues.

There is humid air trapped underneath the plastic housing

Humidity is not supposed to slip underneath the plastic housing of the rear and brake lights.

If you notice condensation underneath the plastic, that means the coverings are not properly set. You will have to remove the plastic housings and wipe away the condensation.

After, replace the plastic back onto the rear light and press on the plastic as firmly as you can without breaking it. You can also apply a mechanic approved sealant to the edges to avoid this problem again.

The bulb is loose

It is very common for a rear bulb light to become loose, especially right after it has just been replaced.

Even mechanics sometimes do not screw in the lightbulb the entire way. Simply screwing in the bulb until it cannot move anymore will fix the issue.

The rear light failure warning system is not working properly

The rear light warning system itself could stop working properly for a couple of reasons. One reason may be that you got into an accident a month or a few months ago and the system is finally feeling the effects of the collision.

May be able to find the reason if you can operate your vehicle’s diagnostic system. Take your vehicle to a mechanic and they will advise you on what to do and what needs to be replaced.


There are a couple of reasons why a vehicle’s rear light failure warning light will turn. Your vehicle’s diagnostic system can provide the reason for the warning light or you can take your vehicle into a mechanic shop.

Some reasons why the light turns on or simple, like a bulb that needs to be replaced. Other reasons are much more difficult to repair, like a system sensor failure.

If one or both of your rear lights do not work, you may be pulled over by the cops. Replace your rear light bulbs as soon as they go out to avoid a ticket. 

  • Eric Williams

    I'm the founder of Daily Car Tips. I wrote articles in the automotive industry for more than 10 years, published in USA and Europe. I love sharing my knowledge and insights with fellow enthusiasts. Join me on this journey as we explore the exciting world of cars together!

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