My driver's side tailight is out again. Seems to be some sort of loose connection as bulb is good. Brakelight works fine. Since I've seen this on at least a dozen other 4 Runners on the road, almost always on the same side, hoping someone's diagnosed this problem already. Any thoughts?

 

I've had this problem myself. The first time I assumed it was the bulb and replaced it. It worked fine for a day or 2, then went out again. Suspicious, I checked the bulb and found that it was good. I sprayed contact cleaner in the socket, wiped the contacts down and put the same bulb in. The problem has not resurfaced in over 9 months.