How do you find the codes for a 97 Nissan Altima?

If you are talking about the computer codes, then with a OBD2 code reader. If you don't have a scanner to read the codes, remove the plastic panel on the center console near the accelerator pedal. you will see the ECU. On your left closest to the firewall there is a screw that may still be covered with cellophane. Turn the ignition switch to run without the engine running. Push through the cellophane with a strait blade screwdriver and turn the screw clockwise until it stops and hold it for two seconds. Turn the screw counter-clockwise and then count the long flashes and short flashes on your check eng light. Write the flashes down on a piece of paper especially if there are multiple codes.