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Home >> Geo >> 1996 >> Prizm Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0300 - Engine Misfire Detected >> Diagnosis & Repair

Diagnosis & Repair

  1. Connect scan tool to DLC. Turn ignition on. Select CLEAR INFORMATION function. Using scan tool, place vehicle into CHECK MODE. Operate vehicle within FREEZE FRAME conditions. If DTC P0300 resets, go to next step. If DTC P0300 does not reset, check for an intermittent problem. See TESTS W/O CODES article.
  2. Check for vacuum leaks at hose connections, EGR valve, PCV valve and intake manifold gasket. Repair as necessary. Retest system. If no problems were found, go to next step.
  3. Install a spark tester at end of each ignition wire, one at a time. Crank engine. If a strong Blue spark is present at each wire, go to step 8). If no spark or weak spark is present, go to next step.
  4. Remove each ignition wire and inspect for carbon tracking or insulation damage. Repair as necessary. Retest system. If ignition wires are okay, go to next step.
  5. Using an ohmmeter, measure resistance of each ignition wire. Replace any ignition wire that exceeds 25 k/ohms. Retest system. If ignition wires are okay, go to next step.
  6. Remove distributor cap and rotor. Inspect for cracks, moisture, poor terminal connections, or carbon tracking. Repair as necessary. Retest system. If no problems were found, go to next step.
  7. Inspect signal rotor inside distributor for damage and correct air gap. Replace distributor if air gap is incorrect. If no problems were found, go to step 15).
  8. Remove and inspect spark plugs. Check for improper gap, cracked ceramic insulators or electrodes. Repair as necessary. If spark plugs are okay, go to next step.
  9. Ensure ignition is off. Install fuel pressure gauge. Note fuel pressure with engine running. If fuel pressure is 31-37 psi (2.2-2.6 kg/cm2 ), go to next step. If fuel pressure is not as specified, go to CIRCUIT TEST A2-7B in BASIC TESTING article.
  10. Check for fuel contamination. Repair as necessary. If fuel is okay, go to next step.
  11. With ignition off, disconnect connectors from all injectors. Install an injector test light (noid-light) on injector harness connector, one at a time. Crank engine. If noid-light does not blink for each harness connector, go to next step. If noid-light blinks at each harness connector, perform CIRCUIT TESTS A2-7C, A2-7D and A2-7E in BASIC TESTING article. Repair as necessary. If no problems were found, go to step 15).
  12. Disconnect noid-light. Using a test light connected to ground, probe power feed terminal (Black/Orange wire) of harness connector which did not blink. Crank engine. If test light comes on, go to next step. If test light does not come on, repair open or short in Black/Orange wire at appropriate injector.
  13. Using a test light connected to battery voltage, probe injector control circuit at appropriate injector harness connector. Crank engine. If test light flashes, go to step 15). If test light does not flash, go to next step.
  14. Check injector control circuits for opens, short to power, or short to ground. Repair as necessary. If control circuits are okay, replace PCM. Retest system.
  15. Check for an engine mechanical problem. If no mechanical problems are found, see TESTS W/O CODES article.
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