With just that single code, I think replacing the sensor will handle it, atleast for a while. Though if you have the time/ability/money to check other things, go ahead. I got my sensor from
www.oxygensensors.com and used the loaner tool from autozone,,, I did it while the engine was hot so it was a PITA, but it doesn't take long and is one of the easier things to do on the zetec, easier than changing the oil.
