First, I'll note that this question can't be answered directly. There wasn't any kind of written code for dealing with people who refused kill orders. Instead, we have to take a look at specific examples of what happened to people who refused and draw conclusions from these cases. In my view doing so shows pretty conclusively that, no, there was no significant consequence for refusing orders. However you'll not find any smoking gun which claims so either way.

There used to be a freely available article titled Those Who Said "No!": Germans Who Refused to Execute Civilians during World War II. Unfortunately the link appears dead now. Here is a jstor link. You can at least read the introduction where Kitterman states confidently: in over 100 examined cases, they were able to find zero instances of someone experiencing the death penalty for refusing such orders. He also claims there were few significant consequences generally.

It's worth noting that this is also true of SS members directly involved in the Holocaust. The 'Cowardly' Executioner: On Disobedience in the SS reflects the same message as the above article: there are no confirmed cases of SS members being significantly punished for refusing to kill. There was also ample reason to locate such cases. During the Nuremberg trials, it was often argued that killing was done from self-preservation. The defense would have been gleeful for any confirmed case of a SS or Wehrmacht personnel being executed for refusing such orders, but despite dozens of trials one has never been produced.

If you can locate the first article, reading both I have referred to in entirety will paint a much better picture than I can here.