1. Check the Obvious:
* Manual Lock: Is the manual lock (the little lever inside the door) working? If not, the problem is likely mechanical, not electrical.
* Door Handle: Is the door handle itself damaged or loose? A broken handle can prevent the locking mechanism from engaging.
* Foreign Objects: Are there any obstructions preventing the door from locking (ice, debris, etc.)?
2. Electrical Issues (Most Likely):
* Power Locks: Test the other doors. If *none* of the power locks are working, the problem likely lies in the power lock system's central control module, fuses, or wiring.
* Driver's Side Specific: If only the driver's side door is affected, the problem is likely with:
* Door Lock Actuator: This is the motor inside the door that actually does the locking. It's the most common culprit. A failing actuator can make a clicking sound when you try to lock the door. Replacement is usually necessary.
* Wiring: Check the wiring harness leading to the driver's side door for broken or frayed wires. This is particularly susceptible to damage from repeated door opening and closing. Look closely at the rubber boot where the wiring enters the door.
* Door Lock Switch: The switch on the driver's side door might be faulty. Try the key fob or the passenger side lock switch to see if the driver's side locks. If they lock using these other methods, the switch is most likely the issue.
* Central Locking System: There's a central control module that manages the locking system. A fault here can cause individual doors or all doors to malfunction. This is harder to troubleshoot without a diagnostic tool.
3. Troubleshooting Steps:
* Check Fuses: Consult your owner's manual to locate the power lock fuse(s) and check for blown fuses. Replace any blown fuses.
* Inspect Wiring: Carefully examine the wiring harness leading to the driver's side door for any visible damage.
* Test the Actuator (Advanced): This requires removing the door panel (plenty of online tutorials show how to do this for a 2000 Ford Explorer). Once the panel is off, you can usually test the actuator directly with a 12V power source (be cautious!). If it doesn't work, it needs replacing.
* Key Fob/Remote: If your key fob isn't working either, the problem may be with the battery in the fob or the car's receiver.
4. Seeking Professional Help:
If you're not comfortable working on car electronics or mechanics, take your Explorer to a qualified mechanic or auto electrician. They have the tools and expertise to diagnose the problem accurately and perform the necessary repairs. They can also test the central locking module if the problem is more widespread.
Remember to always disconnect the negative battery terminal before working on any electrical components in your vehicle. Safety first!
