1. Make sure the gas cap is properly tightened and closed.
2. Start your Scion Tc and let the engine run for a few minutes.
3. Turn off your Scion Tc.
4. Disconnect the negative terminal of the battery for at least 5 minutes.
5. Reconnect the negative terminal of the battery.
6. Start your Scion Tc and let the engine run for a few minutes.
The check engine light should now be reset.
If the check engine light does not reset, you may need to take your Scion Tc to a mechanic to have it diagnosed and repaired.