2004 Toyota Sienna 6 cyl Front Wheel Drive Automatic 20K miles
I have a 2004 Toyota Sienna. One day while filling the gas tank, I left the gas cap off for a little longer than usual, as I was waiting for a receipt. When I replaced the gas cap and then drove off, the check engine light came on and stayed on for the remaining 2 hours of my trip. I cannot be sure if the gas cap was the cause. The engine does not sound or feel like there is anything at all wrong with it. When I park my car at home, I disconnect the negative battery terminal. The following day, more than 12 hours later, I reconnected the battery and drove off to run errands. At first, the check engine light did not come back on. But after driving for a while, it did come back on and stayed on until I drove home. This has happened over and over several times. I disconnect the battery and the next day when I connect it again, the light does not come on at first, but does come on after a while.
So I’m wondering what’s going on. My manual says that if it’s the gas cap, the appearance of the check engine light can take several trips to clear. The main point is that I’m trying to avoid an expensive diagnostic testing at a shop.