1. A computer-implemented method of optimizing a diagnostic test sequence to diagnose a failure mode of a vehicle, comprising: determining a group of diagnostic tests related to a symptom from a pool of diagnostic tests; conducting a probabilistic failure mode analysis determining the efficacy of each of the diagnostic tests based on historical outcomes of actual diagnostic testing; analyzing a comparative utility of each diagnostic tests based on a plurality of factors that can affect problem resolution; assigning a weight to each factor involved in the probabilistic failure mode analysis; ordering the diagnostic tests based upon at least one of: a probability of the diagnostic test identifying a cause of the failure mode in a minimum amount of time; a probability of the diagnostic test identifying the cause of the failure mode at a minimum cost; and a relative weighting of minimizing time versus minimizing cost; and selecting a first diagnostic test from the group based at least in part on the probabilistic failure mode analysis and the weighted factors involved therein.