Q: Check engine light comes on on 2005 Hyundai Elantra

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
was told rear oxygen sensor needs to be replace but after driving for a while check engine light comes on again.
(1) Answer
(3) Comments
And the returned code is the same as before O2 sensor replacement? What code (P----#) is present?