1. Check the Tail Light Switch:
* Location: The tail light switch is usually located on the steering column. It's a small switch that's activated when the vehicle is shifted out of Park.
* Testing: You might need a multimeter to test for continuity across the switch when the key is off and the vehicle in Park. If it shows continuity when it shouldn't, the switch is faulty. A bad switch can cause a constant power feed to the taillights.
2. Inspect the Wiring Harness:
* Look for damage: Carefully examine the wiring harness leading to the tail lights. Check for:
* Chafing or abrasion: Wires rubbing against metal parts can cause shorts.
* Broken or frayed wires: These can create intermittent or constant connections.
* Corrosion: Especially at connectors. Clean any corrosion you find.
* Trace the wires: Follow the wiring from the tail lights back towards the fuse box and under the truck. Look for any areas where wires may be pinched or damaged.
3. Check the Body Control Module (BCM):
* Role: The BCM controls many electrical functions in your Silverado. A faulty BCM can cause various electrical issues, including malfunctioning lights.
* Diagnosis: This is the most difficult part to troubleshoot without specialized diagnostic tools. You might need to consult a mechanic or use an OBD-II scanner capable of reading BCM codes.
4. Fuse and Relay Inspection (Less Likely):
* Fuse Box: Though you've replaced bulbs, a blown fuse related to the tail lights (or even a short causing the fuse to blow repeatedly) is still a possibility. Check all fuses in the relevant sections of the fuse box, noting the amperage rating.
* Relays: Relays are less likely to be the culprit, but a faulty relay could also be providing constant power.
5. Grounding Issues:
* Poor ground connection: A bad ground connection can cause electricity to flow unexpectedly. Check the ground wires connected to the tail light assemblies and the body of the truck. Clean any corrosion and ensure a good metal-to-metal contact.
Troubleshooting Steps:
1. Start with the simplest: Begin by checking the tail light switch and then inspecting the wiring harness.
2. Visual inspection: Look for any obvious signs of damage before using a multimeter.
3. Use a multimeter: If you suspect a short, a multimeter can help you identify the problem areas in the wiring. Test for continuity and voltage where appropriate.
4. Safety first: Always disconnect the negative battery terminal before working on the electrical system.
When to See a Mechanic:
If you're not comfortable working with car electrical systems or you cannot find the problem after thoroughly checking the above, take your Silverado to a qualified mechanic. They have the tools and expertise to diagnose more complex issues like a faulty BCM or a more hidden short in the wiring. A BCM issue is the most expensive fix, so try the easier steps first.
