My high beams will not work anytime I pull the lever to flash someone or just keep them on but, if I pull the lever while the truck is in park they all of the sudden work. Yesterday a friend of mine and I were swapping out my interior dome light and map light with LEDs. He happened to have some extra LED bulbs for the headlights so we decided to try and swap them out. We changed the high beam bulb with an LED and again it only worked when the truck was in park so we decided to just go ahead and switch the passenger side high beam also since it looked a little better although still not fully functional. This is where another weird thing happens. The truck is completely off. I have no key in the ignition, when he unplugs the passenger side high beam to install the LED, my right high beam turned on by itself. He then plugs the bulb back in and now the high beam turns back off. Ive checked the fuses and they are fine so I have no idea how to fix this or what it could be. Any help is greatly appreciated. Btw I have a 2007 silverado classic. Thank you all!

 

Just guessing here, but does the body control module operate the headlights in any way?

 

I'm not certain it does because im not very familiar with wiring but from what I was able to gather from google, I would believe it is.

 

Check grounds. The way gm has their grounds layed out when one goes bad damn trucks do weird things.

 

Thank you, ill make sure to check those when im out of work.

 

It's a grounding issue. The high beams are negative side switched and it's possible to have them on without having anything else on, if the negative wire hits chassis/other negative at the wrong point.