Sit inside your car and insert your key into the ignition. If the car alarm goes off and the key is the original ignition key for the vehicle, you may have a problem only the dealership can solve.
Sometimes low voltage from the car battery or a near-dead battery will cause a glitch in the alarm system. Sometimes, all that needs to be done is to unhook the negative battery cable from the battery and reconnect it. If you accidentally left on one of the accessories to the vehicle, that can lead to a battery drain as well. If you have an after-market alarm installed, make sure the batteries on your receiver unit and the remote are both fresh. Consider changing the batteries to eliminate them as part of the potential problem.
If you have to disable your alarm prior to entering and starting the vehicle, make sure you are close enough to the vehicle to disable the alarm and there is nothing else in the pathway between you and the vehicle that might interfere or cancel the radio signal.
Consult the vehicle owner's manual for alarm troubleshooting. If you can find the manufacturer of your car alarm, contact the manufacturer for specific clues on what to do with the alarm to fix it without taking it to the dealer. Otherwise, the dealer will be the only resort to fix the problem.
