I have new style toyota previa, done 80,000 miles. About half a year ago the little engine warning light came on, we took it to our dealer who said there was nothing wrong and turned it off. It has come back on and been turned off many times with no problem found. Now we have come to sell the car and really need light off, the main dealer said they had new software in to update the EMS but i would like to know what is causing this problem, any help would b greatly appreciated. Thanks