What To Do If Rear Light Failure Warning Light Is On?

Has the rear light failure warning light come on? The indicator for rear light failure is triggered when a change occurs in the current drawn by the taillight. It is most often due to a bulb in the process of wearing out.


The rear light fault indicator looks like a car with the lights on. When it comes up on the car’s dash or instrument panel, it is prudent to check out which lights on your vehicle have failed.

What Does Rear Light Failure Warning Light Mean?

The warning lights on your dash aim to alert you about broken or failing light bulbs at the rear of your car. Taillights and the other bulbs back there are crucial signals when you are on the road. They help you communicate with other drivers sharing the road with you.

If the rear light failure symbol appears when the headlight switch goes to the ON position (at the first or second click stop), it indicates that one or more of the taillights have burned out. If it comes on when the brake pedal is depressed, one or more stoplights have burned out. With any more lights near the back, one of them failing could also make this indicator light up.

rear light failure warning light

The defective bulbs need replacement as soon as possible.

What Causes This Indicator To Appear?

The rear light failure warning light can switch on for a few reasons. Most of them have to do with defective or damaged light bulbs at the rear of the car. If you are going to diagnose the problem, look out for the following potential issues.

1. Taillights

Put the key into your car and start it up to battery power. You don’t need the engine running to check this problem out. Turn on the headlights. If the taillight failure indicator appears now, one or more of your taillights are not functioning correctly. The next step is to go back and look at the taillights. Identify which one isn’t on, and you have your culprit.

faulty taillights can light up the rear light failure warning indicator

While you can still drive a car with a broken taillight, it is judicious to change the bulb. Especially if you drive a car at night, a missing taillight could lead the driver behind you to mistake you for a motorcycle. On the highway, an overtake without enough clearance would spell the end of your car because the overtaking vehicle thinks you are narrower than you are.

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Replacing the bulbs of the taillights is quite an easy job; there is nothing to worry about it. Make sure the replacement bulb is compatible with your car. A new bulb costs about $5 to $10.

In case none of the taillights is broken or burnt out, we have a solution for that as well. It could be that one of them is nearing the end of its life without any outward sign. Keep reading through this article to find out what to do.

2. Brake Lights

Next, you are going to check the brake lights. Turn off the headlights. Then depress your brake pedal. If the warning light comes up this time, you have faulty brake lights. The solution is the same as with the taillights. Once the bulb undergoes replacement, the indicator will turn off.

Driving with defective brake lights is extremely dangerous, endangering your vehicle and its occupants. The cars behind you will not know when you are stopping. Hence, they may end up crashing into your automobile.

What causes brake light failure? There are quite a few different reasons for that. We have another article about malfunctioning brake lights. Do check it out. Now, you might think, can I change a brake light myself? Of course, you can.

3. License Plate Lights

If the warning light stays on all the time, the offender could be the license plate lamps. Cars nowadays have lamps that illuminate the registration or license plates at their rear. We tend not to pay much attention to these illuminators, but they also wire into the warning light. A broken license plate light could be causing the indication on the dash.

These little lamps do not play a vital role in the functioning or safety of your vehicle. However, depending on the laws of your area, it could be illegal to drive at night with the license plate not visible. So, exercise caution and get the bulb changed.

4. Side Marker Lights

Some models of cars have side marker lights. They exist to aid the automobiles outdoor aesthetics. That doesn’t prevent them from being another failure point on the whole. If you are baffled by the warning indicator staying on even when you have changed other bulbs, this could be the reason why.

A fault in these bulbs would trigger the rear light failure warning light either intermittently or continuously. It depends on whether the sidelights go on alongside the brakes or are always on.

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5. If All Lights Appear Fine

Have you checked out all the bulbs and found no burnouts? One of those bulbs has probably neared the end of its working life. It is just not giving any outward signs. If that is indeed the case, the easiest solution is to keep on driving the car. Rather than replace bulbs in a hit and miss method, wait a couple of weeks. Let the warning light stay on.

Sometime soon, the failing bulb will finally give up, and you will know which one to change. Until that point, keep checking the bulbs regularly.

Another possibility is a poor connection setting off the warning light, even though the bulb is working. Unscrew the bulbs and clean the attachments as well as the sockets. If you see some mild corrosion on the socket, scrub it off with sandpaper.

6. Burnt Out Fuse

A popped fuse in the wrong place can send an incorrect signal to the warning light. Make sure to check out the fuses of your car. You will need a digital or analogue multimeter and pointed nose pliers to remove the burnt one.

Once you find the burnt fuse, merely replace it with a new one. Car fuses are too cheap to be sold singly. You can buy about 30 to 40 pieces together for $2 or so.

7. Software Glitch

If you have tried all the steps above without finding the fault, it could be a glitch in the electronic control module. On the other hand, you may have replaced all the broken bulbs and still find the indicator ON. In both cases, resetting the warning lights will help.

a glitch in the ECU can light up the rear light failure warning

While it is possible to reset the lights yourself, it is best if a professional mechanic does it.

8. Internal Short In The Wiring

Unfortunately, the wiring is a complex situation. It is not something you can effortlessly fix at home. If you finally figure out that a short in the wiring is responsible for your troubles, consult an experienced mechanic.

Can You Drive With A Warning Light On?

Yes, there is no restriction to driving even if the warning light has come on. However, the indicator light appears for a reason. So it is prudent to check out the problem before you continue to drive the vehicle.


If you follow these steps, you can efficiently ascertain why the rear light failure warning light is making itself known. In most cases, a quick bulb replacement solves it all. You can find OEM or aftermarket spares in any automobile shop or even online. As long as the new bulb is compatible with your car, you should have no problem.

If you require help in disassembling anything, you can talk to a mechanic from any local garage. Any friend of yours who knows about automobiles can help you out as well.

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