[Kar]

Make sure you don't have ManualVehicleEngineAndLights enabled
Make sure the world time is set to a day hour (8 - 20) (24hour clock)

Step 1:

turn on your vehicle lights while in the vehicle ( you don't see any lights )

Step 2:

exit the vehicle ( the lights are turned on )

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So Basically, if ManualVehicleEngineAndLights isn't enabled, the vehicle lights don't show unless the world time is night
I waited, at the 21st hour, the lights turned on

if ManualVehicleEngineAndLights was turned on, then the lights would show at any world time

Note: I used 'SetWorldTime' with this, I don't know if it had any effect.