Why Does My Trunk Open By Itself? 5 Possible Reasons

Having your trunk open on its own can be frustrating, and allow others access to your car even if it is locked. With so many moving parts, it can be difficult to know where to start. However, there are a few primary reasons that your trunk is opening by itself.

Your car trunk may be opening by itself because the emergency release is stuck, the latch is bent, or there is a problem with the body control module (BCM) or relay. It is also possible that accidentally pressing the key fob or driver’s side release is causing the unwanted opening.

Read on to learn more about five reasons why the trunk of your car may be opening by itself.

1. The Emergency Release Is Stuck

Since 2002, car manufacturers have been required to place an emergency release button in the trunk of every car. The release is a safety feature that prevents people from becoming stuck in the trunk.

Older cars may have a release cord, which is less likely to become stuck. Emergency release buttons are easier to depress accidentally if an object is sitting against them. In addition, the button could get depressed once, and become physically stuck in that position even after the pressure is gone. 

The emergency release mechanism is generally in the back of the trunk and is easy to spot because it is glow-in-the-dark. If you don’t have access to your car’s manual, you can take a look at night or in a dark area. Once you find the button or cord, simply see if they are activated.

2. The Latch Is Bent

The trunk of a car is secured with a latch, which involves two pieces. On the trunk door, there is a stationary piece of metal called a striker. Opposite the lock on the car, there is a latch. When you close the trunk, the latch catches the striker and holds it until you open the trunk again.

If there is a problem with the latch, it will not hold the striker securely. This can cause the trunk to seemingly open by itself. You can check the striker piece to make sure it is not bent, although the striker is rarely the problem.

Likely, part of your latch has become bent. In order to hold the striker, the latch piece should be vertical. You can use almost any type of tool you have available to slowly bend the latch back into place.

Here is a video to show you what that adjustment looks like:

After straightening the latch piece, you should hear a clicking sound when you close the trunk. This confirms that the two pieces have connected.

3. Problem With the Body Control Module

The Body Control Module, or BCM, is one of the main control units in your car. The BCM acts as a hub to control many of the mechanisms in your car, including the trunk.

If the problem with your trunk is caused by the BCM, there will often be malfunctions with other electronic devices.

The BCM controls things like:

  • dash lights
  • headlights
  • horn
  • power windows
  • radio
  • windshield wipers

If any of these other systems are affected in addition to the trunk, the BCM is likely the problem. Sometimes the check engine light will also come on to indicate a problem with the BCM.

Once you confirm the module is the source of your problem, your best option is to replace it entirely. BCM units have become less expensive in recent years, although the exact price is determined by your vehicle.

4. The Relay Is Not Working

If you are not experiencing any other mechanical problems, the BCM may not be to blame. Instead, you should look at the relay. The relay connects the trunk latch to the BCM. It takes the signals from the trunk latch and turns them into ‘on’ and ‘off’ signals. If there is a disruption that causes the signal from the latch to weaken or stop, the relay will send inaccurate messages to the BCM.

Here is the easiest way to test your relay without any tools or gadgets:

  • Locate the relays. Relays look like little boxes and are typically grey or black. Often, the relays in your car will be located in the fuse box. If you cannot find them, check your manual.
  • Identify the trunk latch relay. The box the relays are in should have a diagram explaining where each relay is located. This information can also be found in the car manual.
  • Swap out the relay. The relays should each have a number on the top. Relays with the same number are identical. To determine whether the relay is a problem, swap the relay with another of the same number (for a mechanism you know is working properly).
  • Check the trunk function. If the trunk latch is functioning properly with a new relay, you can be confident that the relay is the problem. This is also true if the mechanism you swapped it with stops working suddenly. For example, if you switched the horn and trunk relays and the horn stops working, you can identify the problem without waiting to see if the trunk stays shut.

If the relay is the problem, you will need to replace it. The easiest way to find a match is to bring the old relay in to an auto parts store and have an associate help you find the correct replacement. 

5. You Are Opening the Trunk Accidentally

Having an easily accessible trunk release can be very handy, but it also comes with the increased risk that you accidentally trigger it. Both the key fob and driver’s dash have convenient trunk releases that are prone to accidental opening.

Key Fob

The trunk button on your key fob is easy to press accidentally. If you keep your car key in your back pocket, sitting down may be enough to trigger the trunk. Additionally, key chain accessories can press the button when in your hand.

The good news is that there is often a way to disable the trunk button on your fob. You can find instructions for doing this in your car’s manual. Often you need to have the key physically in the trunk lock to change the settings.

Driver’s Side Release

There is also a trunk release located left of the steering wheel. The release is a button or lever near the driver’s door that can typically be found on the lower portion of the dash. 

Oftentimes, drivers will unintentionally hit this button with their knee when getting in or out of the car, or adjusting the seat. This is especially true for taller drivers, whose longer legs put their knees in the perfect position to pop the trunk.

The ability to deactivate the driver’s side trunk release is different across car brands, so you should check your manual for your car’s respective instructions.

In Summary

There are several reasons that your car trunk may be opening by itself. Luckily, there are just as many solutions.

Your car trunk may be opening by itself because of a:

  • stuck emergency release
  • bent latch
  • bad BCM
  • dead relay
  • accidental key fob or driver’s side release pressure

You can fix an unpredictable trunk by:

  • releasing the emergency release button or cord
  • repairing a bent trunk latch
  • replacing the BCM
  • replacing the relay
  • disabling the key fob button
  • disabling the driver’s side release

If you get stuck, your car’s manual and local professionals are great sources of information.

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