Trip

The ability for a diagnostic test to run depends largely upon whether or not a trip has been completed. A trip for a particular diagnostic is defined as a key ON cycle in which all of the enabling criteria for a given diagnostic has been met, allowing the diagnostic to run during vehicle operation. This is followed by a key OFF period of sufficient duration to allow the PCM to power down. The requirements for trips vary as they may involve items of an unrelated nature, such as driving style, length of trip, ambient temperature, etc. Some diagnostic tests run only once per trip (e.g., catalyst monitor), while others run continuously (e.g., misfire and fuel system monitors). If the proper enabling conditions are not met during a given ignition cycle, some tests may not be completed, while other tests may not run.