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Home >> Saturn >> 2000 >> LS Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0300: Engine Misfire Detected >> Diagnostic Procedures
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Diagnostic Procedures

  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. Operate engine for one minute. Monitor scan tool display. If any misfire DTCs failed this ignition cycle, go to next step. If no misfire DTCs failed this ignition cycle, problem is intermittent. See DIAGNOSTIC AIDS .
  3. Check if any other injector or ignition DTC is set. If any injector or ignition DTC is set, diagnose affected DTC first. If no other injector or ignition DTC is set, go to next step.
  4. Using scan tool, note current misfire counts. If cylinders No. 2 and 3 or cylinders No. 1 and 4 misfire counts are dominant, go to next step. If cylinders No. 2 and 3 or cylinders No. 1 and 4 misfire counts are not dominant, perform fuel pressure test, injector leakdown test or injector balance test. Check spark plugs, internal mechanical engine failure or fuel grade. See appropriate SYSTEM & COMPONENT TESTING article.
  5. Turn ignition off. Remove EI module from coil assembly, leaving EI module harness connector connected. Connect a test light across suspect coil terminals. Crank engine. If test light does not flash, go to next step. If test light flashes, check ignition coil assembly terminal tightness. Repair as necessary.
    6. NOTE: Do not hold jumper to battery for more than 2 seconds.
  6. Turn ignition off. Disconnect PCM harness connector J1. Turn ignition on. Connect a jumper wire between battery and suspect IC circuit (Orange or White wire). See WIRING DIAGRAMS article. Observe test light. If test light does not flash, go to next step. If test light flashes, check for terminal tightness. Repair as necessary. If terminals are okay, replace PCM.
  7. Check suspect IC circuit for short to ground, open circuit or short to voltage. Repair as necessary. If circuits are okay, check for terminal tightness. Repair as necessary. If terminals are okay, replace PCM.
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