Toyota Repair Problems? Ask a Mechanic for Answers ASAP
Hello, thanks for posting
there are quite a few malfunctions of the engine control or emission control system that can cause the check light to turn on, in most cases emission related and may not affect drivability to a noticeable degree, so if it's running normally it's most likely an emission control related issue, if you recently got fuel make sure the fuel cap is on tight, Check under the hood for any vacuum hoses that may have been disconnected from the air filter or the evap canister.
Other than that I would need some diagnostic code information, trouble codes that are stored in the computer, most autoparts stores like autozone, O Reilly etc can help you get the code numbers and they do this at no charge in most states (not California). then you can just reply back here to me with the code information and I'll continue to assist further.