Mazda 6 Brake Lights Not Working? Let’s Fix That Together

Last Updated on 2025-09-08

Okay, so the brake lights on your Mazda 6 are malfunctioning? You’re in luck because this is a common issue and, fortunately, it is usually easy to fix. Personally, I’ve dealt with this issue way too many times, and I’ll guide you step-by-step so you don’t waste time looking for nonexistent problems. We can check everything from the bulbs, fuses, wires...you name it. Let’s get started.

Step One – Let’s Start With the Obvious Stuff

Believe me, I have seen people completely dismantle their entire trunk only to find out that it was simply a blown bulb. So let’s go through some basic checks first.

check-the-wiring-that-goes-to-a-brake-light

Bulbs First, Always

Remember to set the parking brake. Access the tail light section by popping the trunk open. Inside a Mazda 6, you’ll typically find dual-filament bulbs such as the 7443. The running lights will make one filament and the brake lights will make another. So yes, the tail lights could be functioning, but the brake portion of the bulb could be burnt out.

Make sure to inspect the bulb and its components, and look at it under decent light. If the filament is broken or the glass is darkened, replace is necessary. Honestly, if you aren't sure, just change both rear bulbs—it isn't costly and greatly reliable.

Useful Note: Don’t use bare hands when handling new bulbs. Use gloves or a rag, as the oil from fingers may lead to malfunction.

Fuse Check – Don’t Skip This

Using your fuse puller and needle-nose pliers, check for used fuses. One is located underneath the hood, while the other is under the dashboard. You should be looking for “STOP,” “BRAKE,” or “TAIL” subheadings. With the owner’s manual and the cover of the fuse box, you should easily locate the correct one.

Take off the fuse and hold it up to the light. If the tiny metal strip inside is broken or burnt, that’s your issue. Just change it with another fuse of the same amp rating. It’s good to keep a few in the glovebox too. One day, you’ll be grateful.

While you’re at it, check the relay as well. The relay is usually labeled TNS (Tail Not Switch) or something along those lines. If it's loose and makes strange noises, it might be worth replacing.

Step Two – Brake Light Switch Could Be the Culprit

This is an area that usually gets ignored. Sitting up by your brake pedal is a small switch that is in close proximity to your brake. The brake pedal completes the circuit with that little switch, so when you step on the pedal, the brake lights illuminate.

If the lights are working every now and then, there’s a chance that switch is faulty. Gradually press the pedal and pay attention to whether a faint click can be heard. If there’s no click, there’s no contact and hence, no brake lights to illuminate.

You can test it with a multimeter if you want to be certain, but they are very inexpensive and simple to replace. It’s a matter of removing two bolts, plug-and-play, and you’re done in under ten minutes.

Sometimes all that is needed is to position the switch correctly. You may try adjusting it so that it is pressed correctly when the pedal rises.

Step Three – Let’s Talk Wiring and Grounds

We are now entering the areas that can annoy you (and by annoying I mean a bit interesting). If everything else such as the bulbs, switch, and fuses have been checked then we can move onto the wiring.

Now lets check the trunk's wiring harness. Inspect the area around the brake bulbs for loose plugs, broken insulation, and corroded connectors. Given the age of the car, a wire may have gotten pinched, excessively rubbed, or scraped raw over time.

A neglected ground connection can bring havoc, It's as if poor negative grounding gives the module control lighting nightmares so check loose areas prone to corrosion around the vehicle frame.

On certain models of the Mazda 6, the brake lights share circuits with turn signals and running lights. If these lights are blinking or malfunctioning then there might be much deeper issues like bad servos or choppy control modules.

Okay, we need to check those lights too. They shouldn't dim when you hit the brakes or flash out of sync. If they are, we might have more complex issues to deal with— but let's not jump to conclusions just yet.

Common Solutions

Swap Out Those Bulbs

Just go ahead and replace them, even if they seem fine. It’s cheaper, and you won’t need to worry about them in the future. Just make sure youhave the correct ones; most Mazda 6 models from 2006 to 2015 usually use 7443. The newer models might have LED assemblies.

Replace the Fuse or Relay

If the fuse is blown or the relay is acting up, go ahead and throw a new one in there. Quick win.

Replace or Adjust the Brake Light Switch

If you’ve checked it and it’s not turning on, then just replace it. Simple solution that would take ten minutes. If it’s working but not properly, an adjustment might help. Make it so that when the foot is off the pedal, it would press.

Patch Up That Wiring

When It’s Time to Swap the Whole Taillight

If your Mazda is older, and the tail light assembly is looking bad or there is water inside the lens, just replacing the whole assembly would be better. This is especially true for LED models, where the bulb cannot be replaced.

I have performed this on a few old Mazdas, and honestly, sometimes it’s quicker than looking for a minute internal problem. If you’re already changing the rear lights, you might as well change the look while you are at it. (Check our mod chart to see if you’re interested in aftermarket options.)

Still Stuck? Might Be Time for a Mechanic

In the event that you have followed all of this and still can’t find the brake lights, then it is possible that a malfunctioning brake illumination circuit (BCM) and an unseen short in the wiring harness is the issue. At this point, it is helpful to hand it off to someone who has a complete diagnostic scanning device alongside electrical schematics.

Final Thoughts – You Got This

Most brake light issues boil down to seeing whether the issue is with the bulbs, fuses, or the switch. The majority of the time (9 out of 10), the reason is something fixable in the driver way using simple tools and a whole lot of patience.

Take it one step at a time, don’t put too much thought into it. After driving around and resolving the issue, make it a point to regularly check the lights—as well as prior to long ventures or after heavy showers.

And hey, if you plan to add mods or aftermarket parts, make sure to check how they interact with your lighting system. Sometimes, low-quality parts can lead to annoying electrical problems that are hard to troubleshoot.