1. Bulbs:
* Check all brake light bulbs: This seems obvious, but it's the most common cause. Inspect both the taillights and the center high-mounted stop lamp (CHMSL, or third brake light). A filament might be broken even if the bulb appears intact. Replace any faulty bulbs with the correct wattage. Use a flashlight to get a good view.
2. Fuses:
* Locate the brake light fuse: Consult your owner's manual to find the fuse box location and diagram. There might be separate fuses for the left and right brake lights, and possibly one for the CHMSL. Check for blown fuses (a broken filament inside). Replace any blown fuses with fuses of the *correct amperage* (again, check your manual).
3. Brake Light Switch:
* This is a likely culprit: The brake light switch is located on the brake pedal assembly. It's a relatively inexpensive and easy-to-replace part. When you depress the brake pedal, this switch closes the circuit, completing the electrical connection to power the brake lights. A faulty switch will prevent the brake lights from working, even if the turn signals are fine. There are many online tutorials showing how to access and replace this switch on a 2004 Silverado.
4. Wiring:
* Inspect the wiring: This is more involved and requires some basic electrical knowledge. Check the wiring harness leading to the taillights and CHMSL for any broken wires, corrosion, or loose connections. Look carefully at the connectors at the back of the light assemblies. A multimeter can help you test for continuity (electrical connection) in the wires.
5. Brake Pedal Position Sensor (if equipped):
* Some vehicles have a brake pedal position sensor that may affect the brake lights. This is less likely than the brake light switch, but it's worth investigating if the other steps fail. Again, a mechanic or online resources specific to the 2004 Silverado can help you determine this component's location and how to test it.
6. Body Control Module (BCM):
* This is the least likely cause, as a faulty BCM would often affect more than just the brake lights. However, if all else fails, a malfunctioning BCM could be the culprit. This is a more advanced problem requiring either a skilled mechanic or specialized diagnostic tools.
Troubleshooting Tips:
* Have a helper: It's much easier to test the brake lights if someone can press the brake pedal while you inspect the lights.
* Use a multimeter: A multimeter is an invaluable tool for testing electrical circuits. It can help you determine if there's power getting to the lights and if the wires are intact.
* Online resources: Search for "2004 Chevy Silverado brake light troubleshooting" on YouTube or online forums for specific guidance and visual aids. Many helpful videos and diagrams are available.
If you're not comfortable working on your car's electrical system, it's best to take it to a qualified mechanic. They have the tools and expertise to diagnose and repair the problem safely and efficiently.
