How to Fix an Acura TL Brake Light Failure

Last Updated on 2025-09-07

So, your Acura TL is having issues with the brake lights. That’s pretty annoying. No matter if you are facing complete brake lights failure, or just one of them not working, don’t fret. The issue can usually be fixed without paying a visit to the garage. I’ve assisted a few guys with this same issue, and this is where we started from.

Initial Inspection

Before tearing the car apart, check the easy stuff. Under the hood, there's a 20A fuse labeled STOP — pop that out and inspect it. Down under the dash on the driver's side, there’s another one, Fuse 9, a 7.5A. Even if they don’t look blown, use a multimeter to be sure. Sometimes they’re sneaky like that.

Then check the brake light bulbs — all of them. That includes the center high mount brake light. Pull them out, look for burnt filaments, and if you're running old halogens, now might be a good time to swap to LEDs. Just make sure they’re compatible or you'll run into hyper-flash issues or bulb-out warnings.

Electrical Checks

Now, if the fuses and bulbs are good, the next suspect is the brake pedal position switch. That guy sits right above the brake pedal. You want to see 12 volts on the white/yellow wire, and when you press the pedal, 12 volts should show up on the white/black wire. If you’re not getting power there, chances are the switch is toast. Replace it — it's a common failure and doesn’t cost much.

Keep in mind, if your car refuses to shift out of park, that’s another sign the brake switch is shot. The shift lock system depends on that signal.

While you're down there, have a good look at the wiring. There’s a notorious connector, “Connector O,” behind the under-dash fuse box. It’s a weak point. I’ve seen it corroded, melted, or just loose. Check it out and follow the wiring from the brake switch to the rear brake lights. If you see cracked insulation, brittle wires, or green corrosion — that’s your smoking gun.

Don’t Forget the Grounds

Bad grounds cause all sorts of weird electrical gremlins. In the TL, some important ground points are back in the trunk area — sometimes under the carpet or near the taillights, even under the spare tire. Make sure nothing’s loose, rusty, or covered in gunk. Give the connections a good cleaning and tighten them down.

Trailer Wiring or Aftermarket Mods? Check That Too

If you’ve installed aftermarket taillights or trailer wiring, you might’ve accidentally introduced a problem. I’ve seen guys splice into the wrong wire or overload the circuit. Double-check all the add-ons and make sure nothing’s crossed or shorted out.

Advanced Troubleshooting

If you’re still stuck after all that, it might be time to grab a multimeter and start checking for continuity across all parts of the brake light circuit — from the pedal switch to the failure sensor, to each light socket.

Rarely, the PCM or ABS modules can be involved, especially if you're seeing ABS lights or traction control warnings. Use a scan tool to pull any codes. A regular OBD-II reader won’t cut it here — you’ll need something that can talk to the body modules.

Repairs and Solutions

Once you find the problem, fixing it is usually straightforward. If it’s a bad switch, swap it out. If a connector’s fried, either replace it or bypass it — but do it clean. Solder the wires, use heat-shrink tubing, and keep moisture out. Avoid crimp connectors unless you’re stuck on the side of the road.

For any wiring damage, don’t just twist wires together and call it a day. Do it right and it’ll last. I’ve seen too many “quick fixes” that just caused more problems down the road.

Wrap-Up: Take Your Time and Be Methodical

Problems with the brake light are annoying, yet if you traverse through the circuit from the front to the back and check each section, you can usually locate the problem with minimal effort. Take your time. In most cases, it’s just a malfunctioned switch, fuse, or broken connector — not some complicated electronic failure.

If, after all this, you still can’t make sense of it? Nothing wrong with asking for reinforcements. New perspectives or a factory wiring schematic can be surprisingly helpful.