I have the same problem with my car. It's a recurring problem and I've been noticing it for about a year now. My check engine light comes on and goes off by itself. It usually comes on right before I need an oil change and once I do the oilchange, it goes off. Last spring I took my car to Toyota to get it serviced. I told them about the check engine light. They said nothing was wrong. But when I took the car, the check engine light wasn't on. This reminds me, it's on now so I'll probably take my car to Toyota this week and get it checked out while the light still is on. Hopefully they don't bullshit me again and say that nothing's wrong because I wanna know why that light keeps coming on. By the way, I know one other guy with the same problem.