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If the vehicle was indeed built with keyless entry from the factory, then a DRBIII scan tool can be used to program a new key fob to it. The fob didn't come with instructions because there is no way to program a fob on this vehicle without a scan tool.
HOW DO I KNOW IF IT HAS KEYLESS ENTRY? IT SHOWS IT IN THE OWNERS MANUEL (WHICH I KNOW ARE KINDA GERNIC)?