Q&A

 Master

It may be the battery. If the battery voltage is too low, the "readiness" will not even try to reset. This voltage can be high enough to start the vehicle, so you'll never know it's a problem.
Here is an article that explains the readiness system. http://repairpal.com/drive-cycle-emissions-readiness

 Master

a drive cycle is a very specific way of driving a car to run the monitors. every car is different and there are specific parameters that have to be met to run the monitor. it is not just driving the car. i suggest you take it to a pro and let them do the drive cycle for you. this is also assuming there is no problems as well.

Good luck

Roy

The evaporative emissions monitor is the most difficult monitor to run. I would suspect that is the monitor that is "not ready". Each monitor has very specific criteria for the computer to run it. Typically the evap monitor is triggered between 1/4 and 3/4 of a tank of gas, after a 30 minute period of driving, after a 6 hour rest period when temperatures are over 50 degrees and less than 100 in order for it to run. Find out which monitors were not ready, then ask your local mechanic what the drive cycle is for your car. If he is not able to answer, go to http://techinfo.toyota.com, sign up for a 2 day access ($15) and locate your vehicle specific "drive cycle"