If your goal is to determine if the job was submitted correctly, JES2 does not provide any feedback to the submitting program, so there is no way the submitting program can provide a useful return code. Even if there was a feedback method, I doubt IEBGENER would be checking.
There is a limited mechanism to get the job ID of the most recently submitted job. Unfortunately, I don't think there is formal documentation for this method, though this link
provides a hint about the mechanism. Its user must be writing Assembler, but the program does not have to be authorized to use it. The TSO SUBMIT command uses this mechanism. I've used this mechanism in past endeavors, though my last try, back in the 1990s, when I was trying to write a batch job submission program failed, though I think the problem I had was more to do with other aspects of the program. In order to do this correctly the program has to locate new jobs in its input, and get the job ID before it starts a new job.
If your goal is to determine if the submitted job ran correctly, you need to use other methods, as enrico-sorichetti states in his previous post.