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HOMESERVICE MANUALSCHEVROLET2001CAVALIER LS, 2.4 TREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 8 (ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - 5.7L)DIAGNOSTIC TESTSDTC P0300-P0308: ENGINE MISFIRE DETECTEDDIAGNOSTIC PROCEDURES
2001 Chevrolet Cavalier LS, 2.4 T

Diagnostic Procedures

2001 Chevrolet Cavalier LS, 2.4 TSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2000 Pontiac Firebird, 2000 Chevrolet Corvette, and 2000 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Start and operate engine at idle. Using scan tool, select MISFIRE DATA LIST function and monitor MISFIRE CUR. COUNTERS (one counter per cylinder). If any of misfire counter is incrementing, go to step  4. If misfire counter is not incrementing, go to next step.
  3. Turn ignition on, engine off. Review FREEZE FRAME and/or FAILURE RECORDS data for this DTC and observe parameters. Turn ignition off for 15 seconds. Start engine. Operate vehicle within conditions required to set this DTC. Using scan tool select DTC option and SPECIFIC DTC option, then enter this DTC. If scan tool indicates that this DTC failed this ignition, go to next step. If scan tool does not indicate that this DTC failed this ignition, see DIAGNOSTIC AIDS .
  4. If only one cylinder is misfiring, go to step  6. If more than one of cylinders is misfiring, go to next step.
  5. Check vacuum hoses for splits, kinks and proper routing. Check for leaks at throttle body, intake manifold, EGR valve or PCV system. Check PCM grounds for proper connection. Check that all injector harness connectors are connected to proper injector/cylinder. Repair as necessary. After repairs, go to step  17. If components are okay, or repair is not necessary, go to next step.
  6. Turn ignition off. Disconnect injector harness connector that corresponds to misfire counter that was incrementing. Connect an injector test light to injector harness connector. Start engine. If injector test light if flashing, go to next step. If injector test light is not flashing, diagnose injector circuit. See appropriate SYSTEM & COMPONENT TESTING article.
  7. Turn ignition off. Reconnect injector harness connector. Disconnect ignition wire to spark plug that corresponds to misfire current counter that was incrementing. Install Spark Plug Tester (J-26792) to spark plug wire. Start engine. If spark is present at spark plug tester, go to step  9. If spark is not present, go to next step.
  8. Check resistance of affected spark plug wire. If resistance is less than 700 ohms, replace ignition wire. If resistance is not less than 700 ohms, go to step  16.
  9. Remove and check spark plug from affected cylinder. If spark plug is okay, go to next step. If spark plug is faulty, go to step  11.
  10. Swap spark plug to another cylinder that is operating properly. Operate vehicle under same conditions that misfire occurred. If misfire moved with spark plug, go to step  15. If misfire is still present at original cylinder, perform fuel injector coil test. See appropriate SYSTEM & COMPONENT TESTING article.
  11. If spark plug is fouled with oil or coolant, diagnose mechanical engine problem. If spark plug is not fouled, go to next step.
  12. Check if spark plug is fouled with gasoline. If spark plug is gasoline fouled, diagnose fuel system. See appropriate SYSTEM & COMPONENT TESTING article. If spark plug is not gasoline fouled, go to next step.
  13. Check spark plug for signs of cracks, wear or improper gap. If spark plug is faulty, go to next step. If spark plug is okay, check fuel injector resistance. See appropriate SYSTEM & COMPONENT TESTING article.
  14. Replace or re-gap spark plug. After replacing or re-gapping spark plug, go to step  17.
  15. Replace faulty spark plug(s). After replacing spark plug(s), go to step  17.
  16. Replace faulty spark plug wire. After replacing spark plug wire, go to next step.
  17. If complaint is due to MIL flashing, perform DTC P0420 or P0430 test. If MIL is not flashing, go to next step.
  18. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step  2.
  19. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.
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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.