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If the theft warning led is flashing rapidly when you turn on the ignition then the anti theft system is preventing the vehicle from starting. First disconnect the negative battery terminal cable for 10 minutes. Reconnect it then lock the vehicle with the key in the driver door. Then un lock it and the alarm should be disarmed. You should then make sure the inertia switch did not trip which is located behind the driver front kick panel. If the vehicle still will not start then the security system will need to be reset and the keys re programmed with the Jag factory tool.