In recent decades, the didactic objectives of translation courses have taken advantage of the intensive research done in the areas of secondary languages and translational criticism and evaluation, in relation to the study of the concept of error and its causes. The author is convinced that the analysis of error has a clear pedagogical benefit in detecting problematic learning areas. This paper proposes to reflect on the criteria that will be used as a guide to not only detect errors, but also to identify their causes and to overcome them. One of the most frequent 'language errors' in direct translation from German to Spanish is used as an example: translation of noun compounds. We will ask ourselves to what extent it is important to determine where the source of the error is, when it happens, and how often it happens. This is an initial and necessary step to be able to proceed in the evaluation of the seriousness of the error. Only an extensive diagnosis will permit an effective didactical remedy.