I have a 2008 Prius. It has been giving me an engine light intermittently while I am driving. My mechanic could not get an error code to show. It mostly happens while braking or while driving a right hand curve on roads at speed. Other than trusting it to a Dealership mechanic, do you have any suggestions as to what might be happening? I am grasping at straws here, but I am hopeful for any information.
I'd suggest you look at your oil level and make sure it's not low. That can trigger an intermittent light while driving
