1994 Cadillac Seville service engine soon

Turn the ignition switch to the on position but dont start the car, now press the hot and cold buttons on the heater control panel at the same time and hold them until you see the computer come on, right over the steering column. Have a pencil and paper because I need you to write down all the codes you see then post them back on the computer and i'll see them and get back with you. To exit from the computer press the auto button it will turn the computer off