Go into the ELS.ini file, and find [POLICE 3] EFLC and change Active = 0 to Active = 1. Do that for [POLICE 4] and any other police cars that need ELS.
You should have something like this in the end:
[ POLICE ]
Active = 1
Halogen_Only = 0
Color_Light1L = 0
Color_Light2L = 0
Color_Light3R = 0
Color_Light4R = 0
Color_Light7L = 3
Color_Light8C = 3
Color_Light9R = 3
Offst_SLights = 0
[ POLICE2 ]
Active = 1
Halogen_Only = 0
Color_Light1L = 0
Color_Light2L = 0
Color_Light3R = 0
Color_Light4R = 0
Color_Light7L = 3
Color_Light8C = 3
Color_Light9R = 3
Offst_SLights = 0
[ POLICE3 ] // EFLC
Active = 1 <----- This needs to be set to 1
Halogen_Only = 0
Color_Light1L = 0
Color_Light2L = 0
Color_Light3R = 0
Color_Light4R = 0
Color_Light7L = 3
Color_Light8C = 3
Color_Light9R = 3
Offst_SLights = 0
[ POLICE4 ] // EFLC
Active = 1 <----- This too!
Halogen_Only = 0
Color_Light1L = 0
Color_Light2L = 0
Color_Light3R = 0
Color_Light4R = 0
Color_Light7L = 3
Color_Light8C = 3
Color_Light9R = 3
Offst_SLights = 0