I have a 2015 challenger and today when I unlocked my car with the sensor under the handle and got in the doors locked and the horn beeped three times and I haven't changed any settings please help!

 

Good day Brett Kelley,

This is what I found in the 2015 Dodge Challenger owner's manual on page 19:

Tamper Alert
If something has triggered the Vehicle Security Alarm in
your absence, the horn will sound three times and the
exterior lights will blink three times when you disarm the
Vehicle Security Alarm. Check the vehicle for tampering.

I hope this helps.

Lyne