I fixed it you need to download the emergency lighting system which is in the scripts section then when you download it you we will see a ELS folder paste it to your gta 5 directory when you download the police car it will come with a VCF file inside is a file called police.xml. You will paste this file in the ELS folder located ELS>pack_default then replace the file police.xml with the new one. Good luck! When You start playing press ctrl+p there will be a black screen on the left bottom corner press l for warning light and k is the same thing as l and j is all the lights when you have all the lights on press g for sirens and press t to change the sirens.