Not knowing anything about the alarm's interface, some are positive trigger, some negative, some are contact closures. Usually the outputs are momentary. e.g. momentary lock, momentary unlock
You may have to provide diode isolation (usually two) or at least an external relay..
Are you activating the car's lock & unlock relay or are you trying to activate the motor directly?
When I did my alarm, I added a switch in the passenger compartment such that I could optionally open the passenger door on unarm.
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