Check Engine light on randomly

Hello, my check engine light came on the other day, just randomly. I have just changed the timing belt, and had an oil change a few months ago. Nothing seems wrong with the car as I drive it. Is there any way that I can diagnose it without buying anything? On my 1990 Camry, I just jumper a connection and the check engine light blinks in a pattern...

Oh it has around 120,000 miles on it. I have checked the gas cap issue, too.


Thanks a lot!

when it come on again, go to Auto Zone and they'll diagnose it and give you the falt code of what the problem is.