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Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Sonoma and 2002 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Using scan tool, check for DTCs. Are there any other DTCs stored? If yes, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Start engine. Using scan tool, monitor misfire current parameter in the misfire data list with a load on the engine. Is misfire counter increasing? If yes, go to step  5. If no, go to next step.
  4. Turn engine off. Using a spray bottle with water, wet down secondary ignition system. Start engine. Using scan tool, monitor the misfire current parameter in misfire data list with a load on engine. Does the scan tool indicate a misfire is present? If yes, diagnose ignition system. If no, go to step  18.
  5. Is misfire random on all cylinders? If yes, go to step  10. If no, go to next step.
  6. Is misfire consistent on a specific cylinders? If yes, go to next step.
  7. Turn ignition off. Connect a Spark Tester (J-26792) to spark plug wire of cylinder indicating a misfire. Start and operate engine at idle. If tester indicates spark is consistent on all tested spark plug wires, go to next step. If spark is not consistent, diagnose Electronic Ignition (EI) system.
  8. Remove spark plug from cylinder that indicate a misfire. Check spark plug. If a problem is found, go to step  17. If no problem is found, go to next step.
  9. Reinstall spark plug. Start engine. Monitor misfire current parameter in the misfire data list. Did the misfires change cylinders? If yes, go to step  15. If no, go to step  11.
  10. Perform fuel system diagnostic. See BASIC FUEL SYSTEM CHECK (GASOLINE) in appropriate BASIC DIAGNOSTIC PROCEDURES article. Repair as necessary. Did you find a problem? If yes, go to step  18. If no, go to step  16.
  11. Perform FUEL INJECTOR BALANCE TEST. See BASIC FUEL SYSTEM CHECK (GASOLINE) in appropriate BASIC DIAGNOSTIC PROCEDURES article. Did you find a problem? If yes, go to next step. If no, go to step  17.
  12. Connect Injector Test Light (J-34730-405) on injector harness connector (PCM side). Crank engine. If injector test light flash for each injector, perform FUEL INJECTOR COIL TEST. See appropriate SYSTEM & COMPONENT TESTING article. If injector test light does not flash for each injector, go to next step.
  13. Using a DVOM, check injector harness for short to voltage between PCM connector and injector connector that failed the test. Is the voltage is greater than 0-1 volt? If yes, go to next step. If no, go to step  16.
  14. Repair short to voltage on injector control circuit. After repairs, go to step  19.
  15. Replace spark plugs. After replacing spark plugs, go to step  19.
  16. Check for contaminated fuel, fouled or damaged spark plugs, faulty ignition coil or connections, restricted exhaust system, or faulty PCM grounds. Repair as necessary. After repairs, go to step  19. If no problem is found, go to next step.
  17. Check for engine mechanical problems. Repair as necessary. After repairs, go to step  19. If no problem is found, see DIAGNOSTIC AIDS .
  18. Perform CKP system variation learn procedure. See CRANKSHAFT POSITION SENSOR SYSTEM VARIATION LEARN PROCEDURE  under PROGRAMMING. After performing learn procedure, go to next step.
  19. Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  20. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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