GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2009 🢒 Vibe - FWD 🢒 Engine 🢒 Engine Controls and Fuel - 2.4L (LAX) 🢒 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 powertrain control module (PCM) uses the crankshaft position (CKP) sensor and camshaft position (CMP) sensor to determine engine misfire. The CKP sensor and the CMP sensor monitor their respective components and evaluate changes in the crankshaft rotational speed for each cylinder. Irregular changes in the crankshaft rotational speed indicate a possible misfire. The malfunction indicator lamp (MIL) illuminates when the misfire rate equals or exceeds a pre-determined count. A misfire rate that is high enough can cause the catalytic converter to overheat under certain driving conditions. The MIL will flash ON and OFF when the conditions for catalytic converter overheating are present.

Conditions for Running the DTC
    • DTCs P0100, P0101, P0102, P0103, P0110, P0112, P0113, P0115, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0220, P0222, P0223, P0325, P0327, P0328, P0335, P0339, P0340, P0341, P0500, P0850, P2135 are not set.
    • The engine speed is between 400-6,400 RPM.
    • The battery voltage is greater than 8 volts.
    • The intake air temperature (IAT) is warmer than -10°C (+14°F).
    • The engine coolant temperature (ECT) is warmer than -10°C (+14°F).
    • The mass air flow (MAF) sensor indicates there is greater than 0.12 gram of air per engine revolution.
    • Throttle position is changing less than 0.5 degrees per every 8 milliseconds.
    • DTCs P0300, P0301, P0302, P0303, and P0304 run continuously once the above conditions are met.

Conditions for Setting the DTC

P0300

    • The rough road counter in the PCM indicates that there are normal road conditions.
    • The PCM detects a crankshaft rotation speed variation indicating a misfire rate on random cylinders sufficient to cause emissions levels to exceed a predetermined value.

P0301, P0302, P0303, P0304

    • The rough road counter in the PCM indicates that there are normal road conditions.
    • The PCM detects a crankshaft rotation speed variation indicating a misfire rate on specific cylinders 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 DTCs.

Conditions for Clearing the DTC

DTCs P0300, P0301, P0302, P0303, and P0304 are Type A 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
    • The scan tool data parameters Engine Speed at Misfire and Load at Misfire are populated and frozen at the time the MIL illuminates. These scan tool displays can be used like additional lines of Freeze Frame data. Review the information located in the Engine Speed at Misfire and the Load at Misfire scan tool parameters. The information can help determine engine operation when the misfire occurred.
    • An intermittent can also be the result of a defective CKP sensor signal rotor. Remove the CKP sensor and inspect the signal rotor through the sensor hole. Check the condition of the signal rotor for nicks, dents, missing teeth, and foreign material. Refer to Crankshaft Position Sensor Replacement.
    • An MAF sensor output that is incorrect may cause the PCM to command the fuel system to go lean. Check the performance of the MAF sensor. If the heated oxygen sensor (HO2S) voltage is fixed low, while the fuel trim is constantly high, check the MAF sensor signal circuit for resistance. High circuit resistance can cause the sensor to read a lower volume of air than actual, resulting in a lean fueling condition that can cause engine misfire.
    • Use the scan tool to perform a cylinder balance test by commanding individual fuel injectors OFF with the engine running--Refer to Powertrain Control Module Scan Tool Information.
    • High resistance in the circuits of the injectors could set a misfire DTC. Test the injector circuits of the affected cylinder(s) for a high resistance if you suspect a condition.

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 34730-2B 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 Upper Engine Noise, Regardless of Engine Speed and Lower Engine Noise, Regardless of Engine Speed.
  2. Observe the DTC information with a scan tool. Verify that DTC P0351, P0352, P0353, or P0354 are not set.
    3. ⇒If the DTCs are set, refer to DTC P0351-P0354.

    Important: 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 incriminating.
  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
    • 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, remove the ignition coil of the misfiring cylinder.
  3. Connect the harness connector of the removed ignition coil.
  4. Install a J 26792 to the spark plug boot of the removed ignition coil.

    5. Important: An erratic or weak spark is considered a no spark condition.

  5. Attempt to start the engine and observe the J 26792 . The spark tester should spark.
    6. ⇒If there is no spark, test the spark plug boot for carbon tracking, corrosion, or water contamination. If the spark plug boot tests normal, refer to Electronic Ignition (EI) System Diagnosis for diagnosis of the ignition system.
  6. Ignition OFF, remove the spark plug from the misfiring cylinder. Verify the following conditions do not exist with the spark plug:
    7. • Gas, coolant, or oil fouled--Refer to Spark Plug Inspection.
    • Cracked, worn, incorrectly gapped--Refer to Spark Plug Inspection.
    ⇒If there is a condition with the spark plug, replace the spark plug.
  7. Exchange the suspected spark plug with the spark plug of another cylinder that is operating correctly.
  8. Engine running, observe the scan tool Misfire Current Counters. The misfire should not follow the spark plug exchange.
    9. ⇒If the misfire follows the spark plug, replace the spark plug.
  9. Disconnect the harness connector at the fuel injector of each misfiring cylinder.
  10. Install a J 34730-2B at the harness connector of a misfiring cylinder.
  11. Engine cranking, verify the injector test lamp flashes ON and OFF.
    12. ⇒If the injector test lamp does not flash, refer to Fuel Injector Circuit Diagnosis.
  12. If all tests are normal, test for the following:
    13. • A lean or rich fuel injector--Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F).
    • 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.