GMC Sierra 1500 Alarm Going Off? (11 Causes & Solutions)

The GMC Sierra 1500 is a best-selling full-size pickup truck.

Like many other vehicles, this model is prone to alarm-related problems.

If your Sierra 1500’s alarm keeps going off, this article is here to help...

Why Does My GMC Sierra 1500 Alarm Keep Going Off?

A GMC Sierra 1500 alarm is typically triggered by a faulty door or hood switch. Other common causes include a weak 12V battery, a faulty BCM, and key fob issues. 

1. Faulty Door Switches

A faulty door switch (aka sensor) can lead to the alarm going off at random by sending incorrect signals to the alarm system.

These switches, also known as sensors, are prone to wear and tear from the frequent opening, closing, and slamming of doors, with the driver’s door experiencing the highest level of wear.

The door latches and switches may accumulate dirt, leading to potential issues. Start by cleaning all door latches thoroughly and applying WD-40 to the latch, working it in to check for improvement.

Inspect the wiring that runs from the car’s body to the door for any signs of damage. Typically, this wiring is encased within a flexible hose located on the hinge side of the door.

If you have concerns that the alarm issues could be linked to the door switch, it’s advisable to ask your dealer to conduct a diagnostic test to pinpoint the problem.

“ … the truck thought the rear door was open (it was not). Faulty sensor. Would go off randomly. Annoying.” – SilveradoSierra.com

2. Faulty Hood Switch

Unwarranted alarm activations can often stem from a faulty hood switch. This is also commonly reported on Chevrolet models.

This electronic switch plays a critical role in the car’s alarm system by detecting whether the hood is open or closed.

Faults, looseness, or dirt accumulation in the switch can result in incorrect signals being sent to the vehicle’s computer, which in turn can activate the alarm unnecessarily.

  • Open the hood and locate the hood switch.
  • Check for any clear signs of damage, rust or loose connections.
  • Give the hood switch a thorough cleaning (with contact cleaner), as dirt and grime can cause issues.
  • With the right tools, you can test the switch with a continuity tester.

If you’re mechanically inclined, consider purchasing a new hood switch online and installing it yourself. Otherwise, it’s recommended to seek help from a local mechanic.

Related: GMC Sierra 1500 Beeping? (14 Causes & Solutions)

3. Drained 12V Battery

A depleted car battery can cause various problems, such as accidental alarm triggering.

It is recommended to have your battery tested for its condition, a service that is often inexpensive or complimentary at locations like AutoZone.

Alternatively, you can conduct a self-assessment using a multimeter (refer to the guide at the end of the article below).

Typically, a functioning 12V battery should register between 12.6 and 12.8 volts, whereas a failing one will show below 12 volts.

“I can tell you that on my previous truck when the battery was going bad the alarm would go off, after I replaced the battery I never had that problem again.” – SilveradoSierra.com

“My 2014 used to do it, ended up being a ground issue. Older batteries also can cause this, voltage drops and causes all sorts of gremlins…” – GM-Trucks.com

4. Loose or Bad 12V Battery Connections

Loose connections on the 12V battery can lead to various electrical glitches, like the unintentional triggering of your Sierra 1500’s alarm system.

  • These connections often accumulate dirt or corrosion over time.
  • The vibrations from regular driving can cause the battery terminals to become loose.

Always make sure to turn off the engine before conducting any battery maintenance.

Follow these steps if you plan to carry out the evaluation independently:

  1. Examine the battery for any indications of damage, dirt, rust, or corrosion.
  2. Detach the battery, starting by loosening the clamp nuts with a wrench.
  3. Always disconnect the negative clamp, identified by a ‘-’ sign, first.
  4. Use a toothbrush soaked in a baking soda and water solution to clean the terminals. Rinse with distilled water and dry thoroughly.
  5. When reconnecting the battery, make sure the connections are secure and tight.

5. Key Fob – Low Battery

Sometimes, alarms go off unexpectedly because the key fob has a low battery. Also, if the fob is dirty, it can cause similar issues.

To fix these problems, clean your key fob inside and put in a new battery. It’s usually better to use a good-quality battery.

  • To open your key fob, stick your prying tool into the slit or gap between the two halves of the outer casing and gently apply upward pressure to pop open the device.
  • Remove the battery.
  • Give the key fob a good clean to remove any dirt or fluff – a cotton swab and some rubbing alcohol should do the trick.
  • Check for damage, rust or loose connection (you may need a new key fob depending on what you find).
  • Be sure to insert the new battery facing the right way up.
  • Assemble the outer casing of your key fob by clamping them back together.

6. Faulty Key Fob

Another reported cause of nuisance alarms on this vehicle is a faulty key fob.

If you have 2 remotes, try taking the battery out of one and use the other for a while.

If the alarm problems persist, and you have tried cleaning the inside of the fob(s) and changing the battery, the best thing to do is speak with your dealer.

7. Incorrectly Installed Aftermarket Alarm and Accessories

Incorrect installation or defects in an aftermarket alarm system or accessory are frequent sources of bothersome false alarms.

Aftermarket alarms are typically far more complex than any factory-installed equipment which makes them more prone to issues.

They may also have been installed by incompetent individuals.

If you are experiencing issues with an aftermarket alarm, the best thing to do is speak with a reputable auto electrician. 

8. Damaged Wiring

Damaged electrical wiring can cause a wide range of problems, it can often be tricky to pinpoint too and you may need to have an auto electrician run some diagnostic tests.

In some instances, rodents may have chewed through an electrical wire.

9. Faulty Body Control Module (BCM)

A faulty body control module can cause a wide range of issues including nuisance alarms.

  • The BCM is in charge of electrical communication from different electronic systems.
  • This includes the alarm system, lock-unlock functions, climate control etc.
  • If you have a faulty BCM you may notice other electrical glitches too
  • This can include intermittent operation of various electrical functions, such as the horn, lights, wipers and instrument cluster dials

The signals sent from the door and hood are sent to the BCM to be interpreted and it is a core part of the alarm system.

The BCM can be connected to a diagnostic scan tool which should uncover any errors or show a lack of communication with the main computer.

If in doubt, speak to your local dealer or a reputable mechanic to carry out the tests for you.

10. Animals Climbing On The Vehicle

If your alarm has been set off in the middle of the night, it may have been by an animal climbing on the vehicle.

States such as Illinois, Indiana, Iowa, Texas, Wisconsin, and Carolina have large wild raccoon populations. 

Have a look for footprints on the hood and the roof. 

If you have a CCTV system, examine the footage. These animals usually appear during the night. 

11. Not Closing Doors, Hood, or Trunk Properly

Something as simple as not properly closing the doors, hood, or trunk will inevitably trigger the alarm.

Make sure to check if you have closed every point of entry of your vehicle to avoid accidentally tripping your vehicle’s alarm. 

Alternative Suggestions

Check for Recalls or TSBs

By entering your car’s VIN number on GMC’s recall page or the NTHSA’s Safety Issues & Recalls page you can determine whether or not there is a TSB or recall for your vehicle and if there is you’ll want to get it addressed.

A recall is issued by a vehicle manufacturer for issues that are safety-related, while a TSB covers components that may be malfunctioning but don’t compromise the safety of the vehicle.

Disconnect the Battery

Sometimes mysterious alarm problems can disappear with a simple reboot, there are no guarantees here but it’s worth a try.

Disconnect the battery for 20 seconds and this resets many of the electronics in the vehicle.

Check For Warning Messages

When the alarm occurs can you see any lights or warning messages on the instrument panel?

This can give a clue as to what’s causing the alarm e.g. ‘Hood Ajar’.

Take it to an GMC Dealership

If needed, take your GMC to the dealership.

Tell them you are NOT paying for a check on what the problem might be.

Ask them if they will check it for free.

Most dealerships and other places do quick/initial diagnosis for no money as they plan to make money for the repair of your vehicle.

If your unit is still under warranty then they should fix and resolve the issue for free.

How to Test the 12V Battery

How to Test the Battery:

  • Before testing, remove the surface charge from the battery, this allows for an accurate reading.
  • Simply turn on the headlights for 2 minutes then turn off.
  • Set the multimeter dial to the ’20 Volts’ setting.
  • Make sure the car is turned OFF.

The multimeter will have a red probe and a black probe.

  • The red probe is for making contact with the positive terminal.
  • The black probe is for making contact with the negative terminal.

Measure across the battery terminals.

  • The meter should display a reading, if the battery is fully charged the voltage should be between 12.2 and 12.6 volts.
  • Anything under 12V and the battery should be charged or replaced.

Related: GMC Sierra 2500HD / 3500HD Alarm Going Off? (11 Solutions)

Sources

Author:

  • Ian Sawyer

    Growing up with a father who was a mechanic I had an appreciation for cars and motorcycles from an early age. I shared my first bike with my brother that had little more than a 40cc engine but it opened up a world of excitement for me, I was hooked. As I grew older I progressed onto bigger bikes and...

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