Alarm horn activates on its own

[GTS13DBW]

Hi all; new to posting questions on this forum, but have followed and been impressed by the wise counsel provided by members over the years.

Anyway, I have a 2015 GTS, 17000mi now. Love the car.

My recent issue: Over the last 2 days, the alarm horn has activated unprompted 3 times. This started yesterday after I parked and locked the car (with my fob) following a nice 40-mi drive. Odder still, each time the activation occurred, the horn blared steadily, not like a normal alarm trip where the horn pulses between beep and silence as the lights flash. Using the fob to disengage (pressing lock/unlock, panic, etc) does not appear to work. Eventually, after about a minute, the continuous horn blare and flashing lights stopped, on its own. First occasion yesterday, twice so far today (with car untouched). Any ideas?

 

[GMVIP]

I have the same issue in my 2013, pressed the horn while driving and wouldn't go off, other times just goes off being parked in garage.

 

[GTS-R 001]

it is because you have a composite hood, if you drive and the composite gets hot or any reason that can make it hot (sitting in the sun) the plunger that tells the alarm that the hood is closed slowly pushed up and the hood bends or lifts a tiny bit, then the car thinks someone opened the hood, see if you can open the hood and either adjust the plunger up, (or superglue a spacer onto the top of it) or adjust the hood down a smidge

this should fix your issues

 

[GTS13DBW]

Thank you very much; interesting. Will try this.

 

[GTS-R 001]

used to be and still is a problem with Seibon and Anderson Composites hoods on Gen 3/4 cars, heat soak, composite material. relaxes due to heat and lunger [pushes its way up to set off alarm.

you can try zip tying the plunger down and see if it still happens