Listings of the Diagnostic Trouble Codes (DTCs) for the various engine control systems covered in this manual are located in this section. When using these charts along with the computer module's self-diagnostic system, remember that a code only points to the 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 components are faulty before replacing them, especially the expensive ones.
Following the DTC listings are code charts which have been are provided to help track down what part of the circuit is at fault for the irregular readings and has caused the computer control module to set a trouble code. The charts should be used along with the information in this section, the engine performance symptom charts and the information in Sections 2, 3, 5 and 6 of this manual, as necessary. Keep in mind that most charts are only valid when the trouble is present. If the trouble is intermittent (often caused by loose or corroded terminals on circuit connections), the chart may lead to a dead end or "Intermittent code" ending in which the exact cause of the fault is still left undetermined. In these cases, check all related vacuum hoses and/or wiring for poor, worn or damaged connections. If bad connections are found, wiggle the connection in attempt to duplicate the fault condition so that troubleshooting may continue. Also, before replacing a computer control module, be ABSOLUTELY certain that the module is at fault. The price of a module is usually quite significant and they are usually NON-RETURNABLE components.
After making repairs, clear the trouble codes and operate the vehicle to see if it will reset, indicating further problems.