look at the antenna ( usually next to rear mirror, or high up by the windshield, it should indicate a model number, with that go to internet to search, you can find it out an alarm system using same type of transmiter to match it. " C2 G* k* W$ t9 Y( y1 fDepends on how many function, one way or 2 ways etc. ( i, E$ K1 s( Z5 f, a1 j! LDo you remember the style and look of the one you lost ?