Today's automobiles are computers on wheels, literally. Nearly every aspect of automobile functions are monitored and controlled by a computer and a network of sensors, circuits, relays, solenoids and the like. Repairing new vehicles requires extensive knowledge of both the mechanical portion of the vehicle as well as the sophisticated electrical and computerized portions of the vehicle. OBD-ll (On-board Diagnostics) vehicles include up to a dozen different subsystems that are regularly monitored by the on-board computer to verify that all subsystems are operating correctly. When a fault in one of the sub-systems occurs, technicians use hand held computers, or scanners, connected to the vehicle's on-board computer to check fault codes, diagnose, and repair the problem. After the required repairs have been made, the vehicles fault code can be cleared. However, the vehicle's OBD-ll system does not return all sub-systems back to a normal state following repairs. Instead, repaired vehicles should be run through a drive-cycle to insure the repairs have been made correctly, and that all vehicle parameters are within acceptable limits. This drive-cycle, is not easily performed on streets and highways, and includes speeds up to 60-mph and intermittent periods at idle. Attempting to perform an OBD Drive-cycle on public roads can be difficult, costly and dangerous. For this is the reason most vehicles are returned to customers with readiness codes that have not been returned to a "ready" state. If the repairs have not been correctly made, the customer must soon return to the station when the "check engine" light Returns.

To complicate matters, most states have recently adopted OBD-ll Emissions for vehicles made in 1996 or later. All state programs will fail a vehicle with a check engine light illuminated, or with readiness codes that are not in a normal, or "ready" state. For this reason, the OBD Drive-cycle mentioned above must be performed on all repaired vehicles so that readiness codes are returned to the "ready" state, and to insure that all repairs made have corrected the problem.