When it comes to sex, there are many schools of thought, however, what cannot be disagreed upon is that sex is usually a part of a healthy relationship. Sadly, by that same token, it cannot be argued that it is also a part of many bad relationships (and sometimes the only part), which is why this particular facet of a codependent relationship can be so difficult.
When it comes to being in a romantic relationship, usually sex eventually becomes a part of it, and when it does, it comes with many benefits for both parties. It's enjoyable, it's good for the body, it's good for your mind, and it is one of the best ways to feel close to someone. However, sex can also be something that is used, abused, and sought after for personal or selfish motives. This we see is often the case of codependent relationships.
One party will begin to believe that because they still have an “active sex life” that there is still love and that they are in a healthy relationship, regardless of how they feeling during or after the process. However, sex should never be a defining characteristic of a relationship, especially not a healthy one. If you find that the only times your partner is close to you is when you're being intimate, there is a good chance that you are in a codependent relationship.