Why your car door won't lock or unlock properly

With technological advancement, car locks have gotten much more convenient. Now, rather than put a key in a cylinder to unlock your car, you can press a button, or even just walk up to the car with a fob or phone in your pocket. With that extra tech, though, comes extra complexity, which means it’s not as easy to pinpoint the issue when something goes wrong.

If you’re having problems getting in and out of your car due to a power lock malfunction, here are a six common reasons why your door locks may not be working.

Why your car door won’t lock or unlock

Key fob battery dead.

A simple battery replacement in the key fob could solve your problem. Batteries are typically a coin type, but consult your owner’s manual for the exact number. (Or remove the dead battery from the fob; the battery size is typically printed on the battery itself. You may need to look in the manual or online to learn how to open the fob.)

Blown fuse.

The next simplest solution could be a blown fuse. Before your take your car to a dealer, checking your power door lock fuse could prevent a costly visit. Your owner’s manual should point you to the specific location of the fuse box, but they are typically located behind a plastic panel near your driver’s side footwell and usually don’t require any tools to remove. Once you’ve removed the fuse box lid, the inside of the lid (or the owner’s manual) should have a diagram showing the functions of various fuses. Look for the one corresponding to the door locks. You might need pliers or tweezers to pull it out (some carmakers supply a pulling tool on the inside of the fuse box lid). See if the small metal squiggle in the center of the fuse is connected or not. A blown fuse will have a noticeable gap. Be sure to replace the fuse with a new one of the same amperage.

Key fob malfunction.

Unfortunately key fobs are a bit more complex than a good old-fashioned key. If the battery isn’t the culprit, you’ll need to take the fob to your dealer to get it diagnosed. They’ll connect it to a computer to check if the fob is still sending out the proper signal. If not, the fob will have to be replaced.

Solenoid malfunction.

When you press the buttons on a key fob, it sends a signal to a solenoid inside your car doors. The solenoid translates the electronic signal to a mechanical action, in this case moving a steel rod that the turning of a key in a keyhole used to accomplish. The solenoid within a door that’s not locking/unlocking will require the removal of the inner door panel to replace.

Rod or connector broken.

Though less likely than an electronic malfunction, there’s always the possibility that one of the aforementioned rods or (more plausibly) plastic connectors has broken. The network of hardware links the switches on the door panel with the inner and outer door handles and locks. Plastic hardens over time and can become brittle, or gunk has seeped into and accumulated in the door via the window’s repeated opening and closing. As with the solenoid replacement, this will require the removal of the inner door panel to diagnose and fix, though if there are any problems they will be visible to the naked eye.

Electrical problems.

If none of the above resolves the issue, there may be an electrical problem. Every electrical component requires a logic board and a wire that can be ultimately traced to a power source (the battery). A malfunctioning logic board or a break in the wire could cause problems. If the lock and unlock function works intermittently, there could be an electrical short in the system due to the plastic insulation of the wire being worn down. If it has ceased to function at all, the wire could be broken.

Remember that almost all cars still have a physical key that can be used to lock and unlock the car. It might be hidden in your key fob or exist as a separate backup that came with the car. You can at least use that to lock your car for peace of mind until you or a professional mechanic can resolve the issue.