Any answers regarding what may be wrong are purely speculative until you are able to read the code. If it's not an OBDII code you may have to do some searching for info on it (once you have the actual code), and you will probably find more info on another board such as Scoobynet where they are familiar with your model.
In the US our OBDII transition year was '96. You might try the info here to retrieve the code, whether or not there is any code stored will be answered at that point assuming the check procedure works-
If the fuel is really that old you may want to drain the tank or at least remove a sample from the bottom and check for water or crud. If you find any, drain the tank completely and flush the lines. That may or may not have anything to do with the light/codes but it's still a good idea for a car that has been sitting with fuel in it.