1. Wiring Issues
* Loose Connections: Check all connections at the tail light assemblies, the wiring harness in the rear cargo area, and the junction block near the driver's side rear wheel well. Make sure all connectors are secure and not corroded.
* Broken Wires: Examine the wiring for any visible breaks, chafing, or damage, particularly where the wiring is exposed to movement or sharp edges.
* Ground Fault: A faulty ground connection can prevent current from flowing through the circuit. Check the ground wire connected to the tail light assemblies and ensure it's clean and making good contact.
2. Switch Issues
* Tail Light Switch (Located on the Steering Column): This switch might be faulty or have a broken connection. To test it, use a multimeter to check for continuity when the switch is in the tail light position.
* Turn Signal Switch: If only one side's tail light isn't working, the turn signal switch could be the culprit.
3. Bulb Issues
* Burnt Out Bulbs: It's possible the bulbs are simply burnt out. Check all the tail light bulbs, including brake lights, turn signals, and reverse lights.
* Incorrect Bulbs: Make sure the bulbs are the correct type and wattage for your vehicle.
4. Relay Issues
* Tail Light Relay: The tail light relay controls the flow of current to the tail lights. A faulty relay can cause them to malfunction.
5. Electrical Short
* Short Circuit: A short circuit can interrupt the current flow to the tail lights. This could be due to a damaged wire, a faulty component, or moisture in the wiring.
Troubleshooting Steps:
1. Visual Inspection: Carefully examine the tail light assemblies, wiring, and connectors for any visible damage or loose connections.
2. Multimeter Test: Use a multimeter to test the continuity of the wiring from the tail light switch to the tail light assemblies.
3. Bulb Check: Replace any burnt out bulbs with the correct type.
4. Relay Check: If you suspect the relay is faulty, swap it out with a known good one.
5. Fuse Check: Double-check all fuses related to the tail lights, even though you've already checked them. It's possible a fuse was misdiagnosed or has become faulty after initial inspection.
Additional Tips:
* Consult a Wiring Diagram: Refer to a wiring diagram specific to your 2003 Chevy Express 2500 to pinpoint the exact wiring pathways.
* Professional Assistance: If you're unable to identify the problem after troubleshooting, consider seeking help from a qualified mechanic.
