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HiCustomer you can normally disarm the alarm from either front door or the trunk. Most likely the door that was opened has a faulty alarm contact in the handle and it didn't signal the alarm. If you lock and unlock the car from a different door you will normally be able to turn it off. The alarm does not disable the car from being started. If you'd like to disable it you can simply unplug the connectors at the alarm module. The module is located in the passenger's side footwell underneath the carpeting and the plastic panel. Just unplug both of the plugs from the module. I've attached a picture of the module to help you identify it. Please let me know if you have any questions.