Maddydaddy

I have a 2010 3.0 V-6 SEL and got a check engine light from the P2270 code. So I bought a Motorcraft O2 sensor and replaced the one under the car right before the cat. The light stayed off for a while, but came back on after a week. Is my sensor defective? Did I replace the wrong one? Is there another possible cause of this code? Thanks in advance for any help. James