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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) sensor 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

P0300-P0304 (Without FX3)

    • The mass air flow is greater than 43-254 mg/stk.
    • The engine speed is between 544-4500 RPM.
    • The change in the mass air flow is less than 28-60 mg/stk.
    • The change in the wheel speed is less than 7-13%.
    • The change in the throttle position is less than 117-703 TPS/sec.
    • The change in the ignition timing is less than 17° crk/stk.
    • The battery voltage is greater than 11 V.
    • The engine coolant temperature is greater than -7.5°C (18.5°F).
    • The ambient pressure is greater than 740 hPa (1.07 PSI).
    • The vehicle is not operating in fuel cut off.
    • The DTC runs continuously when the above conditions are met.

P0300-P0304 (FX3)

    •  DTC P0016, P0106, P0107, P0108, P0117, P0118, P0335, P0336, P0340, P0502, or P2110 is not set.
    •  The system voltage is between 11-16 V.
    •  The engine is running for greater than 30 s.
    •  The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

The ECM detects that 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

DTC P0300, P0301, P0302, P0303, and P0304 are Type A or E DTCs.

Conditions for Clearing the DTC

DTC P0300, P0301, P0302, P0303, and P0304 are Type A or E 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 tyre 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
       - A damaged reluctor wheel
    • 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.
    • A misfire may only occur when the engine is under a load or when the engine is cold.

Reference Information

Schematic Reference

Engine Controls Schematics : Siemens ECM - LPG with LCP → Siemens ECM - Gas without FX3 or LCP → Delphi ECM - FX3

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 34730-405 Injector Test Lamp

For regional equivalent tools, refer to Special Tools.

Circuit/System Verification

    Note: Perform the Crankshaft Position System Variation Learn

  1. Verify that no other DTCs are set.
    2. ⇒If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Engine running at the normal operating temperature, verify there is no abnormal engine noise.
    3. ⇒If there is an abnormal engine noise, refer to Symptoms - Engine Mechanical .

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

  3. Engine running, disconnect one fuel injector connector at a time to isolate the misfiring cylinder. The engine speed should change when an injector is disconnected.
  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 .
    • Low fluid level
         ⇒If you find any of the above conditions, repair as necessary.
  2. Ignition OFF, disconnect the harness connector at the appropriate fuel injector.
    3. • Q17A Fuel Injector 1
    • Q17B Fuel Injector 2
    • Q17C Fuel Injector 3
    • Q17D Fuel Injector 4
  3. Connect the J 34730-405 lamp or equivalent between the control circuit terminal 2 and the ignition circuit terminal 1 of the appropriate fuel injector.
  4. Engine idling, the test lamp should flash.
    5. ⇒If the test lamp does not flash, refer to DTC P0261, P0262, P0264, P0265, P0267, P0268, P0270, or P0271 : FX3 → Without FX3 for further diagnosis.
  5. Ignition OFF, connect the fuel Injector connector.
  6. Ignition OFF, disconnect the spark plug wire from the misfiring cylinder.
  7. Install the J 26792 tester or equivalent to the boot of a spark plug wire and ground.

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

  8. Attempt to start the engine and verify that the J 26792 tester spark tester sparks.
    9. ⇒If there is no spark, test the spark plug wire for less than 30,000 Ω. Replace the spark plug wire if greater than the specified range. If the spark plug wire tests normal, refer to Electronic Ignition System Diagnosis for diagnosis of the ignition coil.
  9. Ignition OFF, remove the spark plug from the misfiring cylinder. Verify the following conditions do not exist with the spark plug:
    10. • 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.
  10. Exchange the suspected spark plug with another cylinder that is operating correctly.
  11. Engine running, disconnect the injector that corresponds to the misfiring cylinder. The engine speed should change.
    12. ⇒If the engine speed changes, replace the spark plug.
  12. If all conditions test normal, test or inspect for the following:
    13. • A lean or rich fuel injector--Refer to Fuel Injector Diagnosis with Special Tool .
    • An engine mechanical condition--Refer to Symptoms - Engine Mechanical .

Repair Instructions
    •  Ignition Coil Replacement
    •  Spark Plug Replacement

Repair Verification
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. 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.
  5. If the DTC fails this ignition, a misfire still exists.
   


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