Coolant temperature sensor replacement

My car was recently having issues with the fans staying on and decreased gas mileage. Check engine light also came on. After some research, the problem seemed to be the coolant temperature sensor, so a new sensor was bought and the old one was replaced.

The engine light has gone off, but shifting still seems to be strange as the transmission almost seems to slip as it was doing prior to the sensor change. Gas mileage also has not gotten better since the sensor was changed.

Any ideas as to what the problem could be? There are no other issues. No lights, no overheating. Nothing. Any help would be greatly appreciated. Thanks.