9. A system comprising: a memory; and a processor to: receive system fault codes, component fault codes, and failure modes; generate a first level model comprising first level causal relationships and first level causal weights between the system fault codes and the component fault codes; generate a second level model comprising second level causal relationships and second level causal weights between the component fault codes and the failure modes; combine the first level model and the second level model to generate a graphical model; and determine, using the graphical model, one or more causal probabilities.
9. A system comprising: a memory; and a processor to: receive system fault codes, component fault codes, and failure modes; generate a first level model comprising first level causal relationships and first level causal weights between the system fault codes and the component fault codes; generate a second level model comprising second level causal relationships and second level causal weights between the component fault codes and the failure modes; combine the first level model and the second level model to generate a graphical model; and determine, using the graphical model, one or more causal probabilities. 10. The system of claim 9 , wherein: the first level causal weights comprise conditional probabilities of the system fault codes given the component fault codes; and the second level causal weights comprise conditional probabilities of the component fault codes given the failure modes.