The GMC Terrain is a rugged-looking compact SUV.
Like many other vehicles, this model can be affected by alarm-related problems.
If your Terrain’s alarm keeps going off, this article is here to help…
Table of Contents
Why Does My GMC Terrain Alarm Keep Going Off?
A common cuase of the GMC Terrain alarm going off randomly is a faulty door or hood switch. Other common causes include accidentally pressing the panic button, battery issues, and incorrectly installed aftermarket accessories.
1. Faulty Door Switches (Sensors)
A faulty door switch (aka sensor) can lead to the alarm unexpectedly activating 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.
Examine the wiring extending from the vehicle’s body to the door for any indications of damage. Usually, this wiring is enclosed in a flexible hose positioned 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.
2. Faulty Hood Switch
Unwarranted alarm activations can often stem from a malfunctioning hood switch, especially on GMC vehicles.
Usually, this switch is integrated into the hood latch mechanism.
This compact yet crucial electronic device plays a vital role in the vehicle’s alarm system by determining 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.
“It’s definitely the hood latch… same happens to mine on a windy day. i know my latch is broken 100%” – TerrainForum.net
“When this happens- the usual culprit is the hood latch. Next time this happens- turn off alarm- and then try to remote start. If it just flashes lights– thats most likely the cause–as remote start will not work if it thinks the hood is open.” – TerrainForum.net
Related: 12 Best & Worst GMC Terrain Years (With Pictures)
3. Drained 12V Battery
A depleted 12V car battery can cause various problems, such as accidental alarm triggering. On various GMC models we’ve researched, the car battery was the culprit behind nuisance alarms.
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 test the battery yourself – refer to the guide at the end of the article.
Typically, a functioning 12V battery should register between 12.6 and 12.8 volts, whereas a failing one will show below 12 volts.
“Your alarm may be noticing a voltage drop in the system from an old crappy battery and it’s thinking someone has opened the door and the dome light has come on. If your battery is more than 5 years old, replace it. This should take care of the problem.” – TerrainForum.net
“You might have low voltage in your battery. If it still happens, I’ll go ahead and disconnect the battery for 30 mins to reset the computer…” – TerrainForum.net
4. Loose or Bad 12V Battery Connections
Inaccurate or insecure connections to the 12V battery can lead to various issues, like the inadvertent triggering of your Terrain’s alarm system.
Over time, dirt or corrosion commonly accumulates on these connections.
Driving regularly can cause the battery terminals to loosen.
Always remember to turn off the engine before doing any battery maintenance.
If you intend to conduct the assessment on your own, adhere to this guide:
- Examine the battery for any indications of wear, such as dirt, rust, or corrosion.
- Detach the battery, starting by loosening the clamp nuts with a wrench.
- Always disconnect the negative clamp, identified by a ‘-’ sign, first.
- Use a toothbrush soaked in a baking soda and water solution to clean the terminals. Rinse with distilled water and dry thoroughly.
- When reconnecting the battery, make sure the connections are secure and tight.
“You might have low voltage in your battery. If it still happens, I’ll go ahead and disconnect the battery for 30 mins to reset the computer…” – TerrainForum.net
5. Key Fob Running on 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 identified reason for unwanted alarms on this vehicle is a malfunctioning key fob.
If you have two remotes, consider removing the battery from one and utilizing the other for a period.
If the issues with the alarm persist, even after cleaning the inside of the fob(s) and replacing the battery, it is advisable to consult with your dealer.
7. Accidentally Pressing the Panic Alarm on Key Fob
Your issue with the alarm could stem from something as straightforward (and easily overlooked) as unintentionally pressing the alarm button on your key fob while it’s in your pocket.
The solution is straightforward – have a dedicated pocket for your car key, separate from objects such as pens, coins, or even other keys.
“For me , with our 11′ [Terrain] the key fob is the issue. It’s either the design or extended range of the thing. I keep my keys in my pocket and quite often end up depressing a button. Set the panic button off, or multiple lock sequences that cause lights to flash and horn to sound or in some cases find the hatch open for who knows how long…” – Forums.Edmunds.com
8. 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, making them more prone to issues.
They may also have been installed by incompetent or untrained individuals.
If you are experiencing issues with an aftermarket alarm, the best thing to do is speak with a reputable auto electrician.
9. Damaged Wiring
Faulty electrical wiring can lead to various issues, and identifying the exact problem can be challenging. You might need to enlist the help of an auto electrician to conduct diagnostic tests.
In some instances, rodents may have chewed through an electrical wire.
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.
Related: GMC Terrain Beeping Problems? (11 Causes & Solutions)
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.
Sources
https://cdn.dealereprocess.org/cdn/servicemanuals/gmc/2022-terrain.pdf
https://cdn.dealereprocess.org/cdn/servicemanuals/gmc/2020-terrain.pdf
https://www.gmc.com/ownercenter/recalls
