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DTC P0300-P0306

DTC P0300-P0306

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

DTC P0305

Cylinder 5 Misfire Detected

DTC P0306

Cylinder 6 Misfire Detected

Circuit/System Description

The engine control module (ECM) uses information from the crankshaft position sensor and the camshaft position 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. Too large a proportion of misfires can cause damage to the 3-way catalytic converter. The malfunction indicator lamp (MIL) flashes when the conditions for catalytic converter damage have been met. DTC P0301 to P0306 correspond to the cylinders 1 to 6. If EC; can can determine that a specific cylinder is misfiring, the DTC for that cylinder will be set.

Conditions for Running the DTC


• DTC P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, or P0338 is not set.

• The engine speed is between 450-6,500 RPM and steady.

• The evaporative emissions (EVAP) leak detection is not active.

• The delivered torque signal is greater than 6 % at idle.

• The delivered torque signal is between 6-21 % with the transmission in drive.

• The engine coolant temperature (ECT) and the intake air temperature (IAT) are greater than -30°C (-22°F).

• The throttle angle is steady.

• DTCs P0300 through P0306 run continuously when the above conditions exist for at least 1,000 engine revolutions, 200 revolutions after the first occurrence.


Conditions for Setting the DTC

P0300

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

P0301, P0302, P0303, P0304, P0305, P0306

The ECM detects a crankshaft rotation speed variation indicating a single cylinder misfire rate sufficient to cause emissions levels to exceed mandated standards.

Action Taken When the DTC Sets


• DTCs P0300-P0306 are Type B DTCs.

• When the MIL is flashing, the injector may be disabled for the misfiring cylinder to protect the catalytic converter.

• Depending on the conditions that set the code, the engine may go into Open Loop.


Conditions for Clearing the DTC


• DTCs P0300-P0306 are Type B DTCs.

• The DTC must pass under the same conditions that were present when the DTC failed.


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

- Transmission operation

- A damaged accessory drive component or belt

• High resistance in the injector circuits can activate a diagnostic trouble code related to a misfire without activating a diagnostic trouble code related to an injector. Test for high resistance in the injector circuits for the affected cylinder if you suspect a problem.


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 26792HEI Spark Tester

Circuit/System Verification


1. Engine idling at the normal operating temperature.

2. If there is abnormal engine noise, refer to Symptoms - Engine Mechanical .

3. Verify that no other DTCs are set.

4. If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

5. Observe the scan tool Misfire Current Cyl. 1-6 parameters. The Misfire Current Counters should not be incrementing.

6. Observe the scan tool Circuit Test Status parameters for the various components. Verify the Circuit Test Status parameters for the components that may cause a misfire display OK or Not Run.

7. Engine idling, perform the cylinder power balance test with a scan tool to isolate the misfiring cylinder. The engine speed should change when each injector is disabled.

8. 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 that the following conditions do not exist:

• 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 .

• Exhaust system restrictions

• If you find any of the above conditions, repair as necessary.

2. Ignition OFF, remove the ignition coil of the misfiring cylinder, but leave the electrical connector connected.

3. Inspect the ignition coil boot for the following conditions:

• Holes

• Tears

• Carbon tracking

• Oil contamination

• water intrusion

• If you find any of the above conditions, repair as necessary.

4. Remove the fuel pump fuse from the fuse block.

5. Install the J 26792 to the boot of the appropriate ignition coil and ground.

6.
Note

An erratic or weak spark is considered a no spark condition.


Attempt to start the engine and observe the J 26792 . The spark tester should spark.

7. If there is no spark, refer to Electronic Ignition System Diagnosis for diagnosis of the ignition coil.

8. Ignition OFF, remove the spark plug from the misfiring cylinder. Verify that the spark plug does not exhibit the following conditions:

• Gas, coolant, or oil fouled-Refer to Spark Plug Inspection .

• Cracked, worn, incorrectly gapped-Refer to Ignition System Specifications (LAU) .

9. 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 idling, observe the scan tool Misfire Current Counter parameters. The misfire should not follow the spark plug exchange.

12. If the misfire follows the spark plug, replace the spark plug.

13. If all conditions test normal, test or inspect for the following:

• A lean or rich fuel injector-Refer to Fuel Injector Solenoid Coil Test .

• An engine mechanical condition-Refer to Symptoms - Engine Mechanical .


Repair Instructions


• Spark Plug Replacement

• Ignition Coil Replacement - Bank 1

• Ignition Coil Replacement - Bank 2


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 and perform the appropriate diagnostic procedure.

6. To verify that the performance of the catalytic converter has not been affected by the condition that set this DTC, perform the Repair Verification for DTC P0420. Refer to DTC P0420 .


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