Following is a listing of the Diagnostic Trouble Code Charts for the various engine control systems covered in this manual. When using these charts along with the ECU self-diagnostic system, remember that a code only points to a faulty circuit, not necessarily to a faulty component. Loose, damaged or corroded connections may contribute to a fault code on a circuit when the sensor or component is operating properly. Be sure that the components are faulty before replacing them, especially the expensive ones. Since many of these codes vary from year-to-year, be sure to refer to the appropriate charts.