Toyota Repair: 1) Check engine light is on...., air filter oil, traction control

Question
1) Check engine light is on. It was on before and  dealer said the gas cap was not on straight. Air filter, oil, coolant are all fine. Engine runs great! 2000 Solara w/ 37,000 K. Is there a way I can determine what the check engine light is signifying?

2) Traction control light came on and will not go off if switch is depressed. The light has come on before but always went off went car was restarted.
Suggestions?

Thank you.

Answer
The trac light will come on if the check engine light comes on first, this doesn't mean there is anything wrong with the trac system it is merely a fail safe function to disable the traction control while the check engine light is on, you will need to hook up an OBDII scantoll to see what trouble codes are stored in the computer, if there is an Autozone store nearby go there you can loan their tool to diagnose the problem yourself at no charge.