GMC Sierra Third Brake Light Not Working (How to Fix)

Are you having issues with your GMC Sierra third brake light not working when you apply the brakes? Are you curious about what’s causing this and how to fix it? If yes, we’ll be happy to help you troubleshoot this issue with your GMC Sierra truck.

GMC Sierra third brake light not working is usually caused by a bad bulb that needs replacement. If the bulb isn’t the problem, there are other culprits to consider such as bad connections, blown fuse, wiring problems, or faulty brake light switch.

In this article, we’ll cover, in full detail, all the potential causes behind your truck’s third brake light not working, what to do if this happens, brake light bulb replacement costs, and more.

GMC Sierra third brake light not working causes

Various factors can contribute to your GMC Sierra third brake light not working. Below, we’ll look at the most common causes behind this problem.

• Bad bulb: The most common reason behind the malfunctioning third brake light on your truck is a burned out bulb. You can easily know if your bulb is blown by checking its appearance. If it appears dark or has a broken filament, then it is likely burned out and needs a replacement.
• Bad connections: Another potential cause for your truck’s third brake light to malfunction is when you have a loose or corroded connection. You’d want to inspect whether your third brake light connections are corrosion-free and secured in place.
• Blown fuse: Your GMC Sierra usually has a fuse that’s dedicated to the third brake light. If this fuse blows, it may also make the brake light stop functioning. Locate the fuse in your car; fuse box and inspect it for damages. If blown, replace it with a new one.
• Faulty wiring: You should also inspect all the wiring connected to your vehicle’s 3^rd brake light. Ensure the wiring has no signs of damage, e.g. exposed insulations or frayed wires. If the wiring has any faults have it repaired as necessary.
• Faulty brake light switch: This switch is responsible for activating all your stoplights when you press the brake pedal. Therefore, in cases where all the stoplights fail to come on when the pedal is pressed, you’d want to check the switch.

What to do if the GMC Sierra third brake light is not working?

If your GMC Sierra center high-mount brake light isn’t working, there are several steps you can follow to find out what’s causing the issue. This will help you determine the best action to take to resolve the problem.

Here are helpful troubleshooting tips to follow:

Step 1. Inspect the 3^rd brake light bulb at the rear of your car to ensure it’s not damaged or burned out. If blown (i.e., the filament inside is broken or the bulb has blackened), get a replacement bulb.

Sometimes the bulb may not be blown but would still cause problems if it is not properly installed. Try unscrewing your bulb and repositioning it correctly to see if it helps solve the problem.

Step 2. Inspect your electrical connections to the third brake light. Make sure they’re secure and corrosion free. In case of any corroded or loose connectors/wires, clean them and reconnect them to see if the problem goes away.

Step 3. Check the fuse related to your truck’s third brake light in the fuse box. If this fuse is blown, replace it with a new one that features the same rating as the old one.

Step 4. If the light still doesn’t work, check the wiring that connects your 3^rd brake light to the rest of your car. If it shows any signs of damage such as wear, frayed wires, etc., have it replaced.

Step 5. If you have gone through all the above steps and none seems to solve your problem, then it’s time to consult a certified auto mechanic. They’ll help with further diagnosis and identification of the problem. The mechanic will then do the necessary repairs and replacements to fix the issue.

Where is the fuse for the 3rd brake light on GMC Sierra?

When you want to inspect the third brake light fuse for your GMC Sierra, you first need to know how to access it.

In some GMC Sierra car models, the brake light is usually situated in the fuse box inside your car on the dashboard, on the driver’s side. Specifically, it is located on the left side of the dash.

However, some models have the fuse for the top mount stop light positioned in the fuse box in the engine compartment, under the hood.

Once you locate the fuse box that carries your brake light, you can then check the wiring diagram or your owner’s manual for more info on the specific fuse for your car’s third brake light.

Check this helpful video for more details on the fuse box location in various GMC Sierra models:

Video:

What makes the GMC Sierra 3rd brake light stay on when the truck is off?

In some cases, the third brake light may malfunction by staying on when your truck is off. Many different culprits can also cause this as discussed below:

• Bad brake light switch: One of the common culprits to consider is a stuck or malfunctioning brake light. This has the potential to make the light stay continually on.
• Wiring issues: This is another potential culprit. Issues such as short-circuiting, incorrect grounding, damaged wiring, wear, etc., can make the light stay on even after turning off your car.
• Bad relay: If the relay responsible for controlling the third brake light is faulty, it may also make the light remain on. The relay may be stuck in the On position, thus allowing continuous power flow to your stop light even when your car is off. This can be a risky situation as it can drain your battery and kill it.

Diagnosing your car by paying attention to the above culprits can help you quickly pinpoint the exact cause of this issue. As we always recommend, you can always get a mechanic to do the diagnosis for you if you’re not comfortable doing it yourself.

What is the GMC Sierra third brake light bulb replacement cost?

If you find that the reason your GMC Sierra third brake light is not coming on is due to a bad bulb, then you’ll need to replace it with a new one.

According to YourMechanic, the cost of replacing the bulb is usually anywhere from $10 to $105, depending on factors such as your location, truck model, and whether you’re doing the replacement on your own or hiring an auto technician to do it for you.

Replacing the bulb is generally a cheap fix. It’s also a pretty easy DIY task and you can do it on your own.

In this case, you will just need to spend money on the replacement bulb, which can cost you about $5 to $20. Just ensure you pick the right bulb for your truck model.

If you’re facing issues with your GMC Sierra’s third brake light not working, it’s worth exploring similar problems with other vehicles. You can learn more about this issue by reading our articles on the Jeep Gladiator 3rd brake light not working and the Dodge Ram third brake light not working. These articles provide insights into common causes and potential solutions for a malfunctioning third brake light. By understanding how this issue manifests in different vehicles, you can gain a broader perspective on troubleshooting and resolving the problem. Feel free to explore these resources for more information and guidance.

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Conclusion

There are many potential causes for your GMC Sierra third brake light to fail to work. The most common ones include a burned-out bulb, a blown fuse, loose or corroded wiring, or faulty third brake light wiring. Note that these are just potential causes and you’ll need to have a thorough diagnosis done on your car to find out the exact cause and determine the best fix for it.

In most cases, a blown bulb usually causes this problem. So you should always start by checking if the current bulb is burned out and replace it as necessary. Next, you should test the fuse to see if it’s blown. Other areas to inspect include the brake light wiring and connections. If you’re uncomfortable diagnosing your truck, we recommend getting an auto mechanic to inspect your car and resolve the underlying problem.