Sounds like a fishing expedition for DUI/DWI to me. His BS excuse for probable cause for the initial stop was just to get a reason to check your info, look in your eyes, and get a whiff of the inside of the vehicle for odor of weed or alcohol. Maybe a quick flashlight look for "in plain sight" evidence................ Coupled with location and time of day.
I had a Mahwah cop do that to me a few times cutting down a backroad to 287. Best part was after the one stop was done before I left I told him he had a headlight out and might want to report it to maint before he pulls someone else over for the same thing.......................
But without question my absolute favorite was getting pulled on 287 at 2:30am on the Wanaque bridge by a Passaic County Sheriffs Officer. I was the ONLY car on the road, was only doing 5-10 over and his lights came on the second I came into is view. He asked "know why I pulled you over" and I answered "Because it is 2:30am, you just finished your coffee, and I was the first car you saw in the last 15min.". He laughed. Then he asked why I seemed "tired" and I said I just got one of the best blow jobs of my life from my gf that I just dropped off. He laughed again, checked my documents, and said "Hope the rest of your night is as good the beginning of it." and off I went.