2003 Honda S2000 Owner's Manual - Page 256

State Emissions Testing Select a nearby lightly traveled major highway where you can maintain a speed of 50 to 60 mph (80 to 97 km/h) for at least 20 minutes. Drive on the highway in 5th. Do not use the cruise control. When traffic allows, drive for 90 seconds without moving the accelerator pedal. (Vehicle speed may vary slightly; this is okay.) If you cannot do this for a continuous 90 seconds because of traffic conditions, drive for at least 30 seconds, then repeat it two more times (for a total of 90 seconds). Then drive in city/suburban traffic for at least 10 minutes. When traffic conditions allow, let the vehicle coast for several seconds without using the accelerator pedal or the brake pedal. If the testing facility determines the readiness codes are still not set, see your Honda dealer. 260 Technical Information