SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSGMC1999FORWARD CONTROL 4.3 W, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P0205-P0351DTC P0301DTC P0301: CYLINDER NO. 1 MISFIRE DETECTED (2.2L "J" BODY & "S" SERIES)DIAGNOSTIC PROCEDURES
1999 GMC Forward Control 4.3 W, Standard

Diagnostic Procedures

1999 GMC Forward Control 4.3 W, StandardSECTION Diagnostic Procedures
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. If any other DTCs are set, diagnose DTCs as necessary before proceeding. If no other DTCs are set, go to next step.
  3. Perform a visual inspection of the following. Check vacuum hoses for splits, kinks and proper routing. Check for leaks at throttle body, intake manifold, EGR valve and PCV system. Check PCM grounds for proper connection. Check injector harness connectors for proper installation. Repair as necessary. After repairs, go to step  6. If no problems are found, go to next step.
  4. Start engine and allow it to idle. Using scan tool, select MISFIRE DATA LIST function and monitor MISFIRE CUR. COUNTERS (one counter per cylinder). If MISFIRE CURRENT NO. 1 counter is incrementing, go to next step. If MISFIRE CURRENT NO. 1 counter is not incrementing, go to step  6.
  5. Turn ignition off. Disconnect fuel injector harness connector. Install Spark Tester (J-26792) to cylinder No. 1 spark plug wire. Remove No. 4 spark plug wire from ignition coil. Connect a jumper wire between ground and ignition coil tower (where No. 4 spark plug wire was). Crank engine and check for spark. If spark is present, go to step  8. If spark is not present, go to step  9.
  6. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. If MISFIRE CURRENT NO. 1 counter is incrementing, go to step  5. If MISFIRE CURRENT NO. 1 counter is not incrementing, go to next step.
  7. If a repair was made after visual inspection was performed in step  3, go to step  30. If no problems were found in visual inspection, see DIAGNOSTIC AIDS .
  8. Remove spark plug from No. 1 cylinder. Replace spark plug with a known-good spark plug. Reconnect fuel injection harness connector. Operate vehicle within misfire conditions as recorded in FREEZE FRAME. If MISFIRE CURRENT NO. 1 counter is incrementing, go to step  13. If MISFIRE CURRENT NO. 1 counter is not incrementing, go to step  22.
  9. Remove spark plug wire from No. 1 cylinder. Using DVOM, check plug wire resistance. If resistance is less than 3000 ohms, go to next step. If resistance is not less than 3000 ohms, go to step  23.
  10. Remove ignition coil from cylinder that did not have spark. Check secondary resistance of coil. If resistance is 5000-8000 ohms, go to next step. If resistance is not 5000-8000 ohms, go to step  24.
  11. Replace ignition coil with a known-good coil. Crank engine and check for spark. If spark is present, go to step  24. If spark is not present, go to next step.
  12. Disconnect and inspect Ignition Control Module (ICM) 6-pin connector. Repair as necessary. After repairs, go to step  30. If connector is okay, go to step  25.
  13. Turn ignition off. Disconnect all fuel injector connectors. Install injector test light on injector harness connector for No. 1 cylinder. Crank engine and observe test light. If test light flashes, go to next step. If test light does not flash, go to step  15.
  14. Perform INJECTOR BALANCE TEST. See FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article. If No. 1 injector is okay, go to step  28. If No. 1 injector is not okay, go to step  29.
  15. Remove injector test light. Connect a standard test light between ground and ignition feed terminal at No. 1 injector harness connector. Crank engine and observe test light. If test light is on, go to next step. If test light is off, go to step  27.
  16. Turn ignition off. Disconnect PCM harness connectors. With test light connected to ground, probe injector driver circuit terminal at No. 1 injector harness connector. If test light is off, go to next step. If test light is on, go to step  26.
  17. With test light connected to positive battery terminal, probe injector No. 1 driver circuit terminal at No. 1 injector harness connector. If test light is off, go to next step. If test light is on, go to step  19.
  18. Inspect PCM connectors for damaged pins, corrosion and loose wires. If connectors are okay, go to step  20. If connectors are not okay, go to step  21.
  19. Repair short to ground in cylinder No. 1 fuel injector driver circuit. After repairs, go to step  30.
  20. Replace PCM. Reprogram replacement PCM. After replacing PCM, go to step  30.
  21. Repair connector or connections as necessary. After repairs, go to step  30.
  22. Replace spark plug. After replacing spark plug, go to step  30.
  23. Replace spark plug wire. After replacing spark plug wire, go to step  30.
  24. Replace ignition coil. After replacing ignition coil, go to step  30.
  25. Replace ICM module. After replacing module, go to step  30.
  26. Repair short to voltage in cylinder No. 1 fuel injector driver circuit. After repairs, go to step  30.
  27. Repair open in ignition feed circuit. After repairs, go to step  30.
  28. Check for a basic engine problem (compression, cam timing, throttle body leak, restricted air flow. etc.). Repair as necessary. After repairs, go to step  30.
  29. Replace defective fuel injector. After replacing fuel injector, go to next step.
  30. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select SPECIFIC DTC function then enter DTC P0301. If scan tool indicates TEST RAN AND PASSED, go to next step. If scan tool does not indicate TEST RAN AND PASSED, repeat step  2.
  31. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, no problem is indicated at this time.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.