Check light on dashboard.?

For the past year the check light on my dashboard kept going off and on. I have taken it to different dealers and they seemed to can not find the problem. I was told not to worry because the car is running perfectly. All the needed diagnostic test were done. it's a toyota corolla1999. I am fed up, what am I supposed to do? Serious answers . No time for jokes or sarcastic comments.

I had a car with a alike problem. We changed the gas cap, oxygen sensor, temp sensor. Nothing worked. After two years of chasing it turned out to be a weak hose on the fuel evap system. Problem was that since the OBD eleven codes where for other things and it can not read vacuum leaks I had to find a shop that could keep wanting to find the real problem. They used a smoke machine to check the evap system and found a small pin hole leak that could because the hose to set the light off at certain times.
Call a couple of Toyota independent shops and ask them if they can test the evap system with a smoke machine.

If it is the check engine light and there is nothing wrong with it, have it disabled if it gives you grief..

Have you tried disconnecting the battery cables in an try to clear the fault? This may work.

The sensor may be broken. I'd have that checked out.

i had a chevy s ten that did that. we just put a part of tape over it. that is no joke, I am serious.

EGR valve maybe. Or, some cars are just programmed to light up at certain milage number so you'll take it in for a tune up. I could think they could know these things although.

as humorous as this sounds do you clime any mountains with the car ???? the difference in the altitude can make your light go off caused by the change in the air, also check the air filter if you have not changed it over that time, some times good dust and dirt will make a difference in the filter and if it gets wet it can make it harder for the air to go threw the filter, the sensor tells the computer its starving for air and sets the light off, attempt to remember what you doed any time it went off and let's know it may help to give us some information

I had a corolla myself, Best little car I ever had, till it gave out. I had the same problem and it turned out to be the EGR valve. Every so many miles, I think it was every 3,000 miles My check engine light came on till I replaced it. It may be worth looking into. Hope you find the problem. Good Luck.

is it the check engine light or is it another light the dealer can be looking at the wrong problem could also be a loose gas cap or intermittent evap system problem I could take it someplace else for a second opinion your dealer can be jerking you around if it's something under warranty and just trying to get you through till the warranty expires or can be something the maufacturer has a problem with and expanded the normal warranty and you dealer doesnt want to fix it free of charge. the auto business is hurting all over now to make profits