1. Check the Bulbs:
* Start with the easiest: This is the most common cause. Replace the brake light bulbs in both the taillights and the high-mounted stop lamp (CHMSL – the third brake light on the cab). Make sure to get the correct wattage bulbs. While you're at it, check the turn signal and running light bulbs too – a faulty connection on one might affect another.
2. Inspect the Wiring and Connectors:
* Look for damage: Carefully examine the wiring harness running to the taillights and CHMSL. Look for any frayed wires, corrosion, or broken connectors. Pay special attention to the areas where the wiring enters the body and the connectors at the taillights themselves.
* Clean connectors: Use electrical contact cleaner and a wire brush to clean any corrosion from the connectors. Reconnect them securely.
3. Check the Brake Light Switch:
* Location: This switch is usually mounted on the brake pedal assembly. It's a small switch that activates when you press the brake pedal.
* Testing:
* Visual inspection: Look for obvious damage or loose connections.
* Ohmmeter test (recommended): Disconnect the switch. With the brake pedal *released*, measure the resistance across the switch terminals. There should be infinite resistance (open circuit). With the brake pedal *pressed*, there should be near zero resistance (closed circuit). If the switch shows continuity (zero resistance) when the pedal is released, the switch is faulty. If it doesn't close when the pedal is pressed, it's also faulty. You can find diagrams online showing the specific wiring colors and locations for your truck model. Caution: Always disconnect the battery negative terminal before testing electrical components.
* Manual test (less precise): With the brake pedal released, carefully observe the wires going to the brake switch. If there is power with the ignition on (12V), the switch is likely faulty, even if you don't have a meter. You may need to test this with a test light and knowledge of the appropriate wire colors.
4. Check the Brake Light Fuse:
* Fuse box location: Consult your owner's manual to find the location of the fuse box (usually under the hood or under the dash).
* Check the correct fuse: The owner's manual will also tell you which fuse is for the brake lights. Visually inspect the fuse for a blown element. Replace with a fuse of the same amperage if blown.
5. Check the Body Control Module (BCM) (Less Likely):
* In some cases, a malfunctioning BCM can cause issues with the brake lights. This is less likely but possible. If all else fails, a professional diagnosis may be needed to check the BCM. Often, a scan tool capable of reading codes from the BCM is required for this.
6. Grounding Issues:
* A poor ground connection can cause the lights to stay on. Check the ground wires connected to the taillight assemblies. Clean any corrosion and ensure a good connection.
Important Notes:
* Safety First: Always disconnect the negative battery terminal before working on any electrical components.
* Wiring Diagrams: A wiring diagram specific to your 1992 Chevy Silverado will greatly assist in troubleshooting. These are often available online through repair manuals or forums dedicated to Chevy trucks.
* Professional Help: If you're not comfortable working with car electrical systems, it's best to take your truck to a qualified mechanic.
By systematically checking these areas, you should be able to pinpoint the cause of your persistent brake lights. Remember to always replace parts with the correct specifications.
