1. The Obvious First Steps:
* Check the Bulbs: This is the most common cause. Inspect both brake light bulbs (and the third brake light, if equipped) for breakage or burnout. Replace them if necessary. Make sure they're the correct type and wattage.
* Check the Fuses: Your owner's manual will show you the fuse box locations and diagrams. Locate the fuse(s) for the brake lights and check for blown fuses. Replace any blown fuses with the correct amperage. *Don't* just replace with a higher amperage fuse – that could cause a fire.
2. More Involved Troubleshooting:
* Brake Light Switch: This switch is usually located near the brake pedal. It activates when you press the brake pedal and completes the circuit to the brake lights. It can wear out, break, or become misadjusted. You can test it with a multimeter to see if it's closing the circuit when the brake pedal is pressed. Replacement is relatively inexpensive.
* Wiring: Check the wiring harness from the brake light switch to the lights themselves. Look for any broken, frayed, or corroded wires. This often happens near the connectors. A visual inspection is crucial, but sometimes you may need a multimeter to check continuity.
* Brake Pedal Position Sensor: Some vehicles use this sensor in addition to or instead of a traditional brake light switch. This sensor tells the computer the position of the brake pedal and activates the brake lights accordingly. A faulty sensor needs replacement.
* Grounding Issues: A poor ground connection can prevent the lights from working. Check the ground wires at the tail lights and the brake light switch. Clean any corrosion and ensure a solid connection.
* Central Control Module (CCM): In some vehicles, a central control module governs the brake lights. If the fuses, switch, bulbs, and wiring are good, a faulty CCM could be the problem. This is a more advanced issue requiring professional diagnosis.
* Tail Light Assemblies: Make sure the tail light assemblies themselves are properly connected and not damaged.
3. Testing with a Multimeter:
A multimeter is the best tool for checking voltage and continuity in the electrical system. You can use it to:
* Test for voltage at the brake light sockets with the brake pedal pressed.
* Check for continuity in the wiring between the brake light switch and the lights.
* Test the brake light switch itself for proper operation.
4. When to See a Mechanic:
If you're uncomfortable working with electricity or if you've checked all the above and the problem persists, it's best to take your Durango to a qualified mechanic. They have the tools and expertise to diagnose more complex electrical issues.
Remember safety first! Disconnect the negative battery terminal before working on any electrical components in your vehicle.
