An OBD II trip is official when all the enable criteria for a given test (Monitor) are met. Because enable criteria vary from one Monitor to another, the definition of a trip varies as well. The trip requirements (criteria) can include seemingly unrelated items such as driving style, the length of the trip, and ambient temperature. A minimum requirement for a trip includes one key cycle, and in most cases, the engine must run for a period of time before the test is enabled.
Vehicle tests vary in length - some are performed only once per trip and some are performed continuously. The Catalyst, EGR, EVAP and Oxygen Sensor tests are performed once per trip. The Component Monitor, Fuel and Misfire tests are performed continuously. An OBD II trip is defined as a "key on-drive-the-vehicle-key-off" cycle in which the vehicle is operated in a manner that satisfies the criteria for a test.