I used to look for the J, but now I just don't know. I have a J Rogue - probably one of the few Japan made nissans. Doing pretty good except for rotor Judder - Which I had fixed at the dealer with NEW rotors and NEW pads and re-man calipers at only 30K miles!)
Our 2005 Rav 4 which was a J VIN car had the rear shock blow and the water pump leaking badly and the clutch and the engine using excessive oil by 50K miles. ( 3 years)
The Yaris J VIN car tossed a front wheel bearing one cold winter morning, and had degrading steering and clogged and leaky #1 cat (TSB on that) in the first year. Also the VVT didn't seem to like ANY oil I put in the CC. That's when I started on here to find out what the "hey!" was going on.
I don't recall much about the Fit, used to eat trans fluid yearly and I hurt the engine with a 1/2 bottle of Liqui-Moly. Cant blame the J-Vin on clueless BITOG additive dosing - I REALLY knew better than top add that mud, but I did it anyway Don't know why.
I feel sorry for blokes who come in here looking for oil advice these days
Most reliable cars bought new were (out of a 70 car sample):
1 (96?) Subaru Impreza Wagon 2.2L
2 (83?) Chevy S-10 2.8 carbureted V6 4 speed w/t
3 (85?) Yugo GV 4speed MT
Most reliable (though unloved) used car:
1970 Buick Electra 225 Convertible w/ 455 V8.
Bullit-proof engine and tranny and rear end.
So, nothing special about the J code at MY house
though you know Consumer Reports surveys post a differing outcome.