P0139, Should I be worried or is the o2 sensor just being temperamental?

Got a P0139 code about a month back and cleared it after seeing that it was for the rear o2 sensor. It didn't come back until about a week ago, and I've since cleared it again to see if it would immediately come back. Rear o2 sensors on some of my previous cars have been temperamental, but I want to know if I should actually be worried about this. Dumped some logs as well. Thanks!

 

The code could be a sensor issue or a faulty cat.

Do you have the factory 1st car? Or a high flow cat? Or catless? It doesn't seem like it's anything serious. As far as I know, the secondary O2 doesn't do much besides make sure the cat is working as it should.

What other mods on the car, and what tune/map? Your ltft is also kinda, especially in datalog 61 where it's in the 15's. That could indicate a vac leak somewhere.

 

Full disclosure: Just bought this from a dealer not too long ago (who bought it from an auction) so I'm still figuring out some of this myself.

High flow cat, CS HPFP internals, KN intake BOV, and something's been done with the fuel injectors. The map that's loaded seems to be a custom one from a shop. Doesn't have much other info on it other than 'RT Tuning mapping for MS3 running 91 octane or higher'.

I've noticed that it will creep up above 15 while idling sometimes, then settle back down gradually.

 

The map if you'd like to see it.

 

as far as the injector stuff, was it injector seals? That's about the only thing I can think of.

I'm not familiar with rt tuning. The high ltft could be a tune issue. hard to tell. I'm also not familiar with the K&N intake. Idk how the size of the maf housing compares to stock but I've read it can be a little problematic to tune.