Since the onset of OBD2 in 1996 it has been imperative that the system provide monitoring of certain sub-systems to maintain emissions. This is done by the vehicle’s computer on a continual basis. These sub-systems are required to be tested with each and every trip. Some of these system require more than one trip to confirm that things are well. The main sub-systems that are monitored are the catalytic convertor efficiency, the EVAP system that contains gasoline vapours, engine misfire, oxygen sensor operation, EGR if equipped. These are all under the term “readiness monitors”.
Most emission testing requires that all the monitors are ready. Some testing facilities will allow one monitor to not be ready.
The Drive-Cycle is a “road test” that places the vehicle in a particular situation that will facilitate the quickest completion of monitor tests. As some of these sub-systems cannot complete their testing until another sub-system has completed, it can take days or even weeks for some monitors to complete. If a vehicle is driven precisely according to the drive-cycle, some can be completed all in less than an hour.