You will need  to drive your Honda Odyssey for at least 200-300 miles through various driving  conditions in order to complete the required Emission Monitors. Your Honda’s emission  monitors are internal self-tests which the Engine Control Unit performs to  ensure your Odyssey is not polluting and is running efficiently. The entire  process of self-testing various emission control systems is called a Drive  Cycle.
HOW TO PERFORM A HONDA ODYSSEY DRIVE CYCLE
The  following is a Honda OBDII Drive Cycle Pattern. (Obey all traffic laws while  performing drive cycles. Perform acceleration steps only on highways)
COLD  START: Begin from Cold Start, and ignition in OFF position for at least 1  hour. Insure your Honda’s fuel tank is between 1/4 and 3/4 full and engine  coolant temperature must be below 122°F and within 11°F of the ambient air  temperature. Do not leave the key on prior to the cold start or the heated  oxygen sensor diagnostic may not run.
IDLE  TIME: Run your Honda’s engine (do not drive) for 2 1/2 minutes with the air  conditioner on and rear defroster on. During this period the ECU will be  running the Oxygen Sensor Heater self-test, Air Injection System Passive Air  test, EVAP Purge "No Flow" test, Misfire Detection.
ACCELERATE:  Turn off the air conditioner and rear defroster and begin driving. As soon as  possible apply half throttle until 55mph is reached. The ECU will now run  self-tests on the Misfire Detection, Fuel Trim, and EVAP Purge Flow.
HOLD  STEADY: Now hold your vehicle speed steady at 55mph for three minutes. During  this time the Oxygen Sensor O2 response, Air Intrusive (AIS System), EGR Flow,  Purge Valve, Misfire Detection, and Fuel Trim diagnostics will be performed.
DECELERATE:  During this step you want to slowly let off the accelerator pedal. Do not brake  or shift your Honda in order to slow down. It is important to let the vehicle  coast along gradually slowing down to 20 mph. The ECU will once again self-test  the EGR System, EVAP Purge System and Long Term Fuel Trims.
ACCELERATE:  Go ahead and accelerate again at 3/4 throttle until 55-60mph is reached. This  will perform the same self tests as during the first acceleration step.
HOLD  STEADY: Hold steady speed once again. This time at 55mph for five minutes.  During this time, in addition to running the self-tests as during the first  HOLD STEADY step, the ECU will perform the catalyst monitor diagnostics. If the  catalyst (Catalytic Converter) is marginal or the battery has been  disconnected, it may take 5 complete driving cycles to determine the state of  the catalyst,or in order to Complete the CAT Monitor.
DECELERATE:  This will perform the same diagnostics as in the first Deceleration. Remember  not to press your Honda’s brake or shift gears during deceleration.
This should complete the  drive cycle on your Honda Odyssey. To ensure all monitors are complete use a  scan tool to view the monitors. You may want to complete the drive cycle 2-3  times.