i am trying to figure out what wires are positive and which are negative.its a factory plug with four wires feeding it.im pretty sure it had a set of two lights on the end (license plate lights) i am installing two leds in the plate bolt holes instead. leds have a red and black wire. they need to turn on when the lights are on. i have an ohmeter/voltmeter. any help will be appreciated i will gladly post pics of the plug if necessary. i will remove the plug and ideally have the ability to plug my leds directly into the factory harness.

 

factory service manual wiring schematics could tell you what all 4 wires do

 

Have you tried the DMM? It will tell you which is positive and which is negative.