Check Driver side fender well near/under the battery. it is located on a stud directly underneath the driver's side battery tray. It is the main grounding node for many circuits: horn, turn signal, and wipers to name a few.
Don’t have to remove the battery tray to see it. In the crevice between the washer fluid reservoir cap and drivers side battery, look straight down, deep down. It is a stud with a ring terminal eyelet on it. It’s actually JUST in front (towards front of the truck) of the driver’s battery tray.