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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 00: Engine Misfire Detected

DTC P0301 00: Cylinder 1 Misfire Detected

DTC P0302 00: Cylinder 2 Misfire Detected

DTC P0303 00: Cylinder 3 Misfire Detected

DTC P0304 00: Cylinder 4 Misfire Detected

Circuit/System Description

The engine control module (ECM) uses information from the crankshaft position sensor in order to determine when an engine misfire is occurring and uses information from the camshaft position exhaust sensor in order to determine which cylinder is misfiring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 00 sets. Under certain driving conditions, a misfire rate can be high enough to cause the 3 way catalyst to overheat, possibly damaging the converter. The malfunction indicator lamp (MIL) will flash ON and OFF when converter overheating, damaging conditions are present and DTC P0300 00 is set. DTCs P0301 00 - P0304 00 correspond to cylinders 1-4. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will set.

Conditions for Running the DTC
    • DTCs P0016 00, P0121 00, P0122 00, P0123 00, P0222 00, P0223 00, P0335 00, P0336 00 or P0502 00 are not set.
    • The engine speed is between 520-6 200 RPM.
    • The ignition voltage is between 11-18 V
    • The engine coolant temperature (ECT) is between -7 to +120°C (+19 to +248°F).
    • The A/C compressor clutch is not changing states.
    • The fuel tank level is greater than 15%.
    • The ECM is not in fuel cut-off or deceleration fuel cut-off mode.
    • The ECM is not receiving a rough road signal.
    • The throttle angle is steady within 10%.
    • The throttle angle is greater than 4% when the vehicle speed is greater than 10 km/h (6 MPH).
    • The transmission is not changing gears.
    • DTCs P0300 00 - P0304 00 run continuously when the above conditions are met.

Conditions for Setting the DTC

The ECM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission or catalyst damaging levels to exceed mandated standards.

Action Taken When the DTC Sets
    • DTCs P0300 00 - P0304 00 are Type A (MIL Flashing) or Type B DTCs.
    • When the MIL is flashing, the injectors may be disabled for the misfiring cylinder to protect the catalyst. Depending on the condition that sets the code, the engine may go into open loop.

Conditions for Clearing the DTC

DTCs P0300 00-P0304 00 are Type A (MIL Flashing) or Type B DTCs.

Diagnostic Aids
    • A misfire may only occur when the engine is under a load or when the engine is cold.
    • A misfire DTC may 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
       - Certain rough road conditions
       - A damaged accessory drive component or belt
       - A damaged reluctor wheel

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
    •  Heated Oxygen Sensor Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL 26792 HEI Spark Tester

For equivalent regional tools, refer to Special Tools .

Circuit/System Verification

Note: Perform the crankshaft position system variation learn before proceeding with this diagnostic procedure.

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

Note: All modules must be powered down or misdiagnosis may result.

  1. Verify that the following conditions do not exist:
    2. • Low fluid level
    • Engine 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 .
    • Gas, coolant, or oil fouled spark plugs
    • Cracked, worn, incorrectly gapped spark plugs
         ⇒If you find any of the above conditions, repair as necessary.
  2. Ignition OFF, disconnect the cylinder 1 spark plug wire from the T8 Ignition Coil.
  3. Install the EL 26792 HEI Spark Tester into the position cylinder 1 of the T8 Ignition Coil and ground.

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

  4. Attempt to start the engine and observe the EL 26792 HEI Spark Tester. The spark tester should spark.
  5. Ignition OFF, remove the spark tester and repeat the test for each cylinder.
    6. ⇒If no spark was detected on any of the T8 Ignition Coil spark plug circuits, refer toFuel System Description for diagnosis of the T8 Ignition Coil.
  6. Ignition OFF, inspect each spark plug. If there is a condition with the spark plug, replace the spark plug.
  7. If all conditions test normal, test or inspect for the following:
    8. • A lean or rich fuel injector
    • An engine mechanical condition--Refer to Symptoms - Engine Mechanical .

Repair Instructions
    •  Spark Plug Inspection
    •  Spark Plug Replacement

Repair Verification
  1. Install any components or connectors that have been removed or replaced during diagnosis.
  2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.
  3. Clear the DTCs.
  4. Turn OFF the ignition for 60 s.
  5. If the repair was related to a DTC, duplicate the conditions for running the DTC and use the freeze frame/failure records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List - Vehicle .
  6. To verify that the performance of the catalyst has not been affected by the condition that set this DTC, perform the repair verification for DTC P0420 00.
   


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