A system includes a diagnostic step module and an optimal diagnostic procedure module. The diagnostic step module is configured to identify diagnostic steps of a service procedure to be performed to diagnose a root cause of a fault on a vehicle based on a diagnostic trouble code identifying the fault, and identify a cost associated with performing each of the diagnostic steps. The optimal diagnostic procedure module is configured to determine an order in which to perform the diagnostic steps that minimizes the cost of diagnosing the fault, and output an optimal diagnostic procedure that indicates the diagnostic steps and the order in which to perform the diagnostic steps.