P1273 Nissan -

Question

I keep getting a P1273 code. I replaced the o2 sensors three times. The front and rear ones with various brand name parts, all of which failed and the service light came on with the same code.
I finally took it to a Nissan Dealer and they said that the computer will only except Nissan parts, so I replaced them both with Nissan o2 sensors , front and rear. I also repaired a small crack in the manifold near the front sensor and cleaned the spark plugs and replaced the idle throttle. I asked the Dealer to reprogram the computer which they did, also, reprogram the idle but said I may need to changer the rear o/2 . I told them that I already did that with their part. They said well maybe your okay then now.
I drove the car about 200 miles and the service light came back on, but I don't get it. The car runs great, no idle problems, no loss of power, no misfires etc. It's just this P1273 code keeps popping up.
The Nissan Dealer wants me to spend $200 on a in depth diagnostic check or trade it in for an up graded pre-owned car. I got five month to decide because that is when my next inspection is due. Is it time to dump the car ( which I don't want to do ) or keep trying to find a solution by spending more money on parts and labor that may not be needed and be a total waste?