An improved scan tool, e.g., for OBD II, for use with vehicle computer networks. The improved scan tool determines the proper protocol to use to communicate with a vehicle computer network. The proper protocol is determined by requesting information from the vehicle computer network using a plurality of protocols and selecting the protocol that returns the most pieces of information. In addition, the improved scan tool determines a communications drop-out with one or more modules and automatically recovers from a the communications drop-out.