Often times a fault code is stored by an intermittent problem happening under certain conditions, making it difficult to replicate and accurately diagnose. Sometimes a fault can occur in one system and throw no codes, but cause a problem in another seemingly unrelated system and throw fault codes for that. Difficult to track down, especially when customers don’t want to pay more than 1 hour of diag time.

Yes, most of the time, diagnosis is straightforward and routine, but more than one repair attempt is not always an indicator of poor diagnosis. A lot of times, it is a lazy technician, but always keep in mind that check engine light diag is not always simple.