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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 258 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0301-P0304: Cylinder Misfire Detected >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 GMC Sonoma and 2003 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. Start and allow engine to operate at idle or operate within the conditions listed in the Freeze Frame/Failure Records. Monitor all of the misfire counters with scan tool. Are any of the misfire current counters incrementing? If yes, go to next step. If no, problem is intermittent.
  3. Are any DTCs other than DTC P0300 set? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, go to next step.
  4. Can any abnormal engine noise be heard? If yes, diagnose for an engine mechanical problem. If no, go to next step.
  5. Turn ignition off. Disconnect the spark plug wire from the spark plug that corresponds to the Misfire Current counters that were incrementing. Install Spark Tester (J-26792) to a good ground. Jumper the spark plug end of the companion cylinder ignition wire to engine ground. The companion cylinder is the cylinder that shares the same ignition coil. Start engine. Does the spark jump the tester gap and is the spark consistent? If yes, go to step  7 . If no, go to next step.
  6. Remove the spark plug wire for the affected cylinder. Inspect the spark plug wire. Measure the resistance of the spark plug wire with a DVOM. Is the spark plug wire resistance less than 3000 ohms per foot. If yes, diagnose electronic ignition system. Refer to ELECTRONIC IGNITION SYSTEM under IGNITION SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L SONOMA & S10 PICKUP article. If no, go to step  15 .
  7. Remove the spark plug from the cylinder that indicated a misfire. Inspect the spark plug. Does the spark plug appear to be okay? If yes, go to next step. If no, go to step  9 .
  8. Exchange suspected spark plug with another cylinder that is operating properly. Operate the vehicle under the same conditions that the misfire occurred. Did the misfire move with the spark plug? If yes, go to step  14 . If no, go to step  12 .
  9. Is the spark plug oil or coolant fouled? If yes, diagnose for an engine mechanical problem. If no, go to next step.
  10. Is the spark plug gas fouled? If yes, go to step  12 . If no, go to next step.
  11. Does the spark plug show any signs of being cracked, worn, or improperly gapped? If yes, go to step  13 . If no, go to next step.
  12. Perform the fuel injector coil test. Refer to FUEL INJECTOR COIL TEST under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 2.2L SONOMA & S10 PICKUP article. Did you find and correct the condition? If yes, go to step  16 . If no, diagnose for an engine mechanical problem,
  13. Replace or gap the spark plug. If an improper gap is found, be sure to gap the spark plugs using a wire type gauge. After regapping or replacing spark plug, go to step  16 .
  14. Replace faulty spark plug. After replacing spark plug, go to step  16 .
  15. Replace spark plug wire. After replacing spark plug wire, go to next step.
  16. Was the customer's concern regarding the MIL flashing? If yes, go to next step. If no, go to step  18 .
  17. Operate engine at 2500 RPM for 4 minutes. Operate the vehicle within the Conditions for Running the DTC. Does the DTC run and pass? If yes, go to next step. If no, go to DTC P0420: TWC SYSTEM - LOW EFFICIENCY  .
  18. 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 .
  19. 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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