Check engine light and code p02270

Hello,

Assuming that you cleared all the codes after changing the sensor and the code came back. This code is essentially saying there is to much air post catalytic and the sensor output is 0 volts. Commonly an exhaust leak. Seeing you've checked for that and the wires are fine and the new sensor is nice and tight then other causes could be faulty fuel pressure or injector. The purge solenoid valve could be acting up as well. It could also have coolant getting where is doesn't belong. How did the old sensor look did it have contamination on it? How about performance, is it running rough?
Tom