2001 Honda Odyssey Owner's Manual - Page 319
2001 Honda Odyssey Manual
Page 319 highlights
Malfunction Indicator Lamp Readiness Codes Your vehicle has certain "readiness codes" that are part of the on-board diagnostics for the emissions systems. In some states, part of the emissions testing is to make sure these codes are set. If they are not set, the test cannot be completed. If your vehicele's battery has been disconnected or gone dead, these codes are erased. It takes several days of driving under various conditions to set the codes again. If possible, do not take your car for a state emissions test until the readiness codes are set. To check if they are set, turn the ignition ON (II), but do not start the engine. The Malfunction Indicator Lamp will come on for 20 seconds. If it then goes off, the readiness codes are set. If it blinks 5 times, the readiness codes are not set. See State Emissions Testing on pages 343 and 344. Taking Care of the Unexpected