The Wrangler immobiliser will only work in the vehicle it has been programmed to accept, it does this by checking the vehicle's VIN number upon first turning on the ignition after having its power disconnected i.e.. Vehicle servicing / flat battery etc.. If the Led stays permanently on when the ignition is switched on, the system will need to check the vehicle for its VIN number and compare with its expected VIN number. During this process, which can take upto 20 seconds, the ignition must be left switched ON. Successful comparison is indicated by the LED extinguishing if the vehicle had previously been unimmobilised or by a rapid flashing showing that the vehicle is immobilised.