How to reset car alarm

You probably have a bad lock on the driver door. This is very common, needs to be tested, and the sensor from the alarm is integrated. The door will sound the alarm if the sensor goes bad. If it is only the driver door that does it, try opening another door with the key. If that doesn't work, the ATA unit, basically the brain of the alarm system, is located under the passenger seat. If it is disconnected the alarm will stop functioning.