I ran into this message when attempting to delete a SQL Job.  Somehow a  subplan was orphaned and not allowing me to delete the job.

First I got the Job_id by right clicking on the job and scripting the drop.

The script will contain the job_id

Now I searched for the Job_id in the System Maintenance sub plans.

I then used the delete statement above to remove the sub plan.  Then I was able to go back to the jobs and delete the job.

Thanks to Moshin’s DBA Blog for help on this.   Moshin’s DBA BLog