I have found that when I give the class a work packet that has real world problems from actual shops with cars that had these problems the students can see that they will be forced to try and solve problems that may not be in a diagnostic manual. This teaches them to look at the symptoms, analyze the information that is presented to them and try to come up to a single conclusion to help diagnois the problem. The students really seem to enjoy this type of brainstorming in their groups and it really shows how well they are getting the covered material.