The other site suggests that 15% of '04 owners experience a check engine light issue. Mine is on for the second time in <200 miles. Any other opinions out there about lights turning off by thenselves?
If the light stays on, take it to Toyota service at your leisure and have them do a computer read out to see what diagnostic codes are set. They should be able to repair it under warranty. If the light goes out, you can still hope for a code read out, but it might have been erased by the time you get there. If it's erased, you may have to wait until it happens often enough to be worth leaving with Toyota service a day or too in hopes that they can catch it on and get the read out.
I would advise you to be very viligent with respect to attending a off to any issue that arises with your Prius. You 2004 owners are pioneering the new model as the 2001-2003 owners have. The comments in this message thread that toyota should be able to attend to any issue that may arise because the of the warranty is only one factor. Your failure to have the/an issue documented as arising within a certain period of time may preclude you from utilizing powerful tools of redress should you later realize an ongoing problem whose beginnings occurred some time ago. The tire wear issue that appeared to plague the 2001-2003 Prius is one such situation. Buy the time folks realize that they have been played - spending their time runing around the known issue - and money, buying new tires in an attempt to overcome the problem, those that realized that they have been played by toyota have not prreserved their right to utilize lemon laws. :? if Consequently, to save face, they lower their standards and complain to the wind while toyota sales, toyota service, and outside tires and alignment centers, count your money and eat your valuable time. There goes your reported gas savings!
You can check the users groups and glean how the/any responses - aside from the no response or arbitration blow off route - by toyota motor corporation to customers escelated concerns has always been to stick to the factory recommendations.
I just picked up my '04 Prius today, and the check engine light came on at about 10 miles on the odometer. Of course, the dealer's service dept was open, but no Prius tech would be there until Monday. I'll have to check the gas cap as mentioned above.
I was informed by my dealer today that they check and the issue was due to a coating on the catalytic converter that would "burn off" at about 50 miles. My check engine light had come on at about 10 miles, and sure enough, it went out at about 46 miles last night.