GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2009 🢒 G3 🢒 Safety and Security 🢒 Immobilizer 🢒 DTC P0300-P0304

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0300: Engine Misfire Detected

DTC P0301: Cylinder 1 Misfire Detected

DTC P0302: Cylinder 2 Misfire Detected

DTC P0303: Cylinder 3 Misfire Detected

DTC P0304: Cylinder 4 Misfire Detected

Circuit/System Description

The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensors in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. A misfire rate that is high enough can cause 3-way catalytic converter damage. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for catalytic converter damage are present.

Conditions for Running the DTC
    • DTCs P0010, P0011, P0013, P0014, P0016, P0017, P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0222, P0223, P0315, P0335, P0336, P0502, P0651, and P2135 are not set.
    • Engine speed is between 450-6,500 RPM.
    • The ignition voltage is between 9-18 volts.
    • The ECT sensor is between -7 and +125°C (+19 and +257°F).
    • If the ECT is less than -7°C (+19°F), misfire is delayed until ECT is greater than 21°C (70°F).
    • The fuel tank level is greater than 10 percent.
    • The ECM is not in fuel cut-off or decel fuel cut-off mode.
    • The throttle angle is greater than 3 percent when the vehicle speed is greater than 5 km/h (3 mph).
    • The automatic transmission is not changing gears while the TP sensor is greater than 95 percent.
    • The manual transmission clutch fuel cut-off is not active.
    • The antilock brake system (ABS) and the traction control system (TCS), if equipped, is not active.
    • The DTCs run continuously when the above conditions are met.

Conditions for Setting the DTC

The ECM detects a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed a predetermined value.

Action Taken When the DTC Sets

DTCs P0300, P0301, P0302, P0303, and P0304 are Type A (MIL flashing) or Type B DTCs.

Conditions for Clearing the DTC

DTCs P0300, P0301, P0302, P0303, and P0304 are Type A (MIL flashing) or Type B DTCs.

Diagnostic Aids
    • A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect for the following possible sources:
       - A tire or wheel that is out of round or out of balance
       - Variable thickness brake rotors
       - An unbalanced drive shaft
       - Certain rough road conditions
       - A damaged accessory drive component or belt
    • High resistance in the circuits of the injectors could set a misfire DTC without setting an injector DTC. Test the injector circuits of the affected cylinder(s) for a high resistance if you suspect a condition.
    • The Hold indicator flashes when there is an engine misfire.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

    • J-26792 Spark Tester
    • J-36012-A Ignition System Diagnostic Harness
    • J 34730-405 Injector Test Lamp

Circuit/System Verification
  1. Engine running at the normal operating temperature, verify there is no abnormal engine noise.
    2. ⇒If there is an abnormal engine noise, refer to Symptoms - Engine Mechanical.
  2. Observe the DTC information with a scan tool. Verify that DTC P0201, P0202, P0203, P0204, P0315, P0335, P0336, P0351, P0352, P0353, or P0354 is not set.
    3. ⇒If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

    Note: A misfire may only occur when the engine is under a load. An engine load may be necessary to verify the condition.

  3. Observe the scan tool Misfire Current Counter parameters. The Misfire Current Counters should not be incrementing.
  4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing
  1. Verify the following conditions do not exist:
    2. • Vacuum hose splits, kinks, and incorrect connections
    • Engine vacuum leaks
    • Crankcase ventilation system for vacuum leaks--Refer to Crankcase Ventilation System Inspection/Diagnosis.
    • Fuel pressure that is too low or too high--Refer to Fuel System Diagnosis.
    • Contaminated fuel--Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
    •  Restricted exhaust system--Refer to Restricted Exhaust.
         ⇒If you find any of the above conditions, repair as necessary.
  2. Ignition OFF, disconnect the harness connector at the appropriate fuel injector.
  3. Connect the J 34730-405 between the control circuit terminal B and the ignition voltage circuit terminal A.
  4. Engine idling, the test lamp should flash.
    5. ⇒If the test lamp does not flash, refer to DTC P0201, P0202, P0203, or P0204 for further diagnosis.
  5. Ignition OFF, connect the fuel Injector connector. Remove the ignition coil assembly.
  6. Inspect the ignition coil spark plug boots for the following conditions:
    7. • Damage
    • Carbon tracking
    • Oil contamination
    • Water intrusion
         ⇒If you find any of the above conditions, repair as necessary.
  7. Connect the harness connector to the ignition coil assembly.

    8. Note: It may be necessary to secure the J 36012-A to the spark plug boots with electrical tape.

  8. Install the J 36012-A to the spark plug boots.
  9. Install the J 26792 between the spark plug boot of the misfiring cylinder and ground.
  10. Connect the remaining wires to the appropriate cylinders.

    11. Note: An erratic or weak spark is considered a no spark condition.

  11. Attempt to start the engine and observe the J 26792 . The spark tester should spark.
    12. ⇒If there is no spark, refer to Electronic Ignition (EI) System Diagnosis for diagnosis of the ignition coil.
  12. Ignition OFF, remove the spark plug from the misfiring cylinder. Verify the following conditions do not exist with the spark plug:
    13. • Gas, coolant, or oil fouled--Refer to Spark Plug Inspection.
    • Cracked, worn, incorrectly gapped
    ⇒If there is a condition with the spark plug, replace the spark plug.
  13. Exchange the suspected spark plug with another cylinder that is operating correctly.
  14. Engine running, observe the scan tool Misfire Current Counters. The misfire should not follow the spark plug exchange.
    15. ⇒If the misfire follows the spark plug, replace the spark plug.
  15. If all conditions test normal, test or inspect for the following:
    16. • A lean or rich fuel injector--Refer to Fuel Injector Balance Test with Special Tool
    • An engine mechanical condition--Refer to Symptoms - Engine Mechanical

Repair Instructions
    •  Ignition Coil Replacement
    •  Spark Plug Replacement

Repair Verification
  1. If the customer concern was a flashing MIL, operate the vehicle within the conditions for running DTC P0420. Refer to DTC P0420.
  2. Clear the DTCs with a scan tool.
  3. Turn OFF the ignition for 30 seconds.
  4. Start the engine.
  5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
  6. If the DTC fails this ignition, a misfire still exists.