Side markers have to be lit when the parking or headlamps(this all three come on(4 literal)) Ford chooses to have a side marker that stays lit and uses a turn signal that is side visible. Gm is a lot more into the use a side marker with the turns and my park avenue is a perfect example of that where the turn is visible front abd side all along it but the rear is a 194 that is polarity switched and does switchback with the front kinda cool Anyway you have a amber turn signal plastic most like