1. Bulbs: The most common cause. Check both the brake light bulbs (there are usually two, one in each taillight) and the center high-mounted stop lamp (CHMSL or third brake light) bulb located on the rear window. They may be burned out or simply loose.
2. Fuse: A blown fuse in the fuse box can interrupt the power supply to the brake lights. Consult your owner's manual to locate the fuse box and the correct fuse(s) for the brake lights.
3. Brake Light Switch: This switch, located near the brake pedal, activates the brake lights when the brake pedal is pressed. If it's faulty, it won't send the signal to the lights. This is a relatively common point of failure.
4. Wiring: Damaged or corroded wiring in the brake light circuit can prevent power from reaching the bulbs. This is less common but possible, especially in older cars. Look for any obvious damage near the taillights or near the brake pedal switch.
5. Brake Light Circuit Issues: A problem within the wiring harness or a short circuit somewhere in the system is possible. This often requires a more in-depth electrical diagnosis.
6. Ground Issues: A poor ground connection can also prevent the brake lights from working. This is less likely but should be considered if other troubleshooting steps fail.
7. Tail Light Assembly: It's possible the issue lies within the tail light assembly itself. There might be a short circuit or internal damage preventing the lights from functioning, even if the bulbs are fine.
Troubleshooting Steps:
1. Check the bulbs: This is the easiest and first step.
2. Check the fuses: Refer to your owner's manual for the correct fuse location and rating.
3. Test the brake light switch: You can usually test this by having someone press the brake pedal while you check for power at the switch's connector (with a multimeter, if you have one).
4. Visually inspect the wiring: Look for any obvious damage or corrosion.
5. If all else fails: Consult a qualified mechanic to diagnose and repair the problem. This is especially important if you're not comfortable working with car's electrical system.
Remember to always disconnect the battery negative terminal before working on any electrical components of your car to prevent accidental shorts or injury.
