Toyota Spacio 2000 with yellow light on

Hello,, friends together with greeting them, since I am new in the forum ... I have a story that I have my first car ,,, is second hand ,, a Toyota Corolla Spacio 2000 engine 1.6, well a yellow light has been turned on, which it seems to me that it shows problems also when it reaches a certain level of fuel, it is marked as if it were full, they the marker problem .. ??
Thanks in advance ...

Check's light the healthiest is to put a diagnosis, the fuel marker, he opened to take it out to check it since these combs are scratched or cut, and if this bad is changed and now.