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Home >> Chevrolet >> 2006 >> Optra LS, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 1.4L DOHC >> Diagnostic Information and Procedures >> DTC P0300-P0304 >> Circuit/System Testing
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Circuit/System Testing

  1. Verify that the following conditions do not exist:
    • If you find any of the above conditions, repair as necessary.
  2. Ignition OFF, disconnect the spark plug wire from the misfiring cylinder.
  3. Install the J 26792  Spark Tester to the boot of a spark plug wire and a good ground. See Special Tools .
    4. IMPORTANT: An erratic or weak spark is considered a no spark condition.
  4. Attempt to start the engine and observe the J 26792  Spark Tester. See Special Tools . The spark tester should spark.
    • If there is no spark, test the spark plug wire for less than 1,000 ohms per 31 cm (per foot). Replace the spark plug wire if more than the specified value. If the spark plug wire test normal, refer to Electronic Ignition (EI) System Diagnosis  for diagnosis of the ignition coil.
  5. Ignition OFF, remove the spark plug from the misfiring cylinder. Verify that the following conditions do not exist with the spark plug:
    • Gas, coolant, or oil fouled
    • Cracked, worn, incorrectly gapped
    • If there is a condition with the spark plug, replace the spark plug.
  6. Exchange the suspected spark plug with another cylinder that is operating correctly.
  7. Engine idling, disconnect the injector that corresponds to the misfiring cylinder. The engine speed should change.
    • If the engine speed changes, replace the spark plug.
    • If the engine speed does not change, test the fuel injector. Refer to Fuel Injector Coil Test .
  8. If all conditions test normal, test or inspect for an engine mechanical condition, refer to Symptoms - Engine Mechanical .
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