Diagnostic Procedures

WARNING: This page is about a different car, the 2001 GMC Savana, 2001 Chevrolet RV Cutaway, 2001 Chevrolet Cutaway, and 2001 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
Install scan tool. If any DTCs other than P0135 or P0155 are stored, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs other than P0135 or P0155 are stored, go to next step.
Turn ignition on, engine off. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 15 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If DTC failed this ignition cycle, go to step 5. If DTC did not fail this ignition cycle, go to next step.
Turn ignition off. Use a spray bottle filled with water to wet down secondary ignition system. Start engine. Monitor misfire counters in misfire data list. If scan tool indicates a misfire is present, repair ignition system as necessary. If scan tool does not indicate a misfire is present, go to step 13.
If misfire is random on all cylinders, go to step 10. If misfire is not random on all cylinders, go to next step.
Turn ignition off. Connect spark tester to spark plug wire of cylinders that indicate a misfire. Start and idle engine. If tester indicates spark is consistent, go to next step. If tester does not indicate spark is consistent, repair ignition system as necessary.
Remove spark plugs from cylinders that indicate a misfire. Inspect spark plugs. If problem was found, repair as necessary. After repairs, go to step 14. If problem was not found, go to next step.
Install spark plugs in cylinders that did not indicate a misfire. Start engine. Monitor misfire counters in misfire data list. If misfires change to other cylinders, go to step 12. If misfires do not change to other cylinders, go to step 10.
Perform fuel system diagnostic. See appropriate SYSTEM & COMPONENT TESTING article. If problem was found, repair as necessary. After repairs, go to step 15. If problem was not found, go to step 13.
Perform fuel injector balance test. See appropriate SYSTEM & COMPONENT TESTING article. If problem was found, repair as necessary. After repairs, go to step 15. If problem was not found, perform fuel injector coil test. See appropriate SYSTEM & COMPONENT TESTING article.
Replace spark plugs. After repairs, go to step 15.
Check for the following conditions in the following order:
- Contaminated fuel.
- Fouled or damaged spark plugs.
- Ignition coil and connections.
- Distributor cap for damage.
- Exhaust Gas Recirculation (EGR) valve for leaks.
- Exhaust system for restrictions.
- PCM grounds.
If problem was found, repair as necessary. After repairs, go to step 15. If problem was not found, go to next step.
Perform CKP system variation learn procedure. See CRANKSHAFT POSITION SENSOR under PROGRAMMING. Go to next step.
Check for engine mechanical problems. See appropriate article in ENGINES. If problem was found, repair as necessary. After repairs, go to next step. If problem was not found, see DIAGNOSTIC AIDS .
Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC runs and passes, go to next step. If DTC does not run and pass, go to step 2.
Using scan tool, observe stored information. If scan tool displays any DTCs that have not been diagnosed, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not display any DTCs, system is okay.