P0301
DTC P0300-P0304
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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 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. 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. DTCs P0301 through P0304 correspond to cylinders 1 through 4. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will set, and the corresponding fuel injector is disabled. The ECM will re-enable the fuel injector after 3 crankshaft revolutions when the misfire is not current. The ECM will re-enable the fuel injector after 6 crankshaft revolutions when the misfire is not current, if the vehicle is equipped with a manual transmission.
Conditions for Running the DTC
* DTC P0010, P0011, P0013, P0014, P0016, P0017, P0068, P00C8, P00C9, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0117, P0118, P0119, P0121, P0122, P0123, P0191, P0192, P0193, P0222, P0223, P0335, P0336, P0340, P0341, P0365, P0366, P0606, P0651, P16F3, P2100, P2101, or P2135 is not set.
* The engine speed is between 450 and 6,600 RPM. OR The engine speed is greater than 1,000 RPM and DTC P0315 is set.
* The engine coolant temperature (ECT) is between -7 and +127°C (19 and 261°F).
* If the ECT is colder than -7°C (+19°F) at start-up, this diagnostic will not run until the ECT is between 21 and 127°C (69 and 261°F).
* The ignition voltage is between 9 and 32 V.
* The evaporative emissions (EVAP) leak detection is not active.
* The ECM is not receiving a rough road signal.
* The fuel level is at least 11 %.
* The ECM is not in fuel cut-off or decel fuel cut-off mode.
* DTCs P0300 through P0304 run continuously when the above conditions exist for at least 1,000 engine revolutions. 200 revolutions after the first failure.
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
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-P0304 are Type B DTCs.
* The ECM disables the fuel injector of the misfiring cylinder when a misfire is present.
Conditions for Clearing the DTC
DTCs P0300-P0304 are 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
- Transmission operation
- A damaged accessory drive component or belt ; remove the belt and safely operate the engine to evaluate
* High resistance in the circuits of the injectors may 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.
* If the condition is intermittent, observing the scan tool IC Circuit Test and Fuel Injector Circuit Test Status parameters may help isolate the condition. The circuit test status parameters will change from OK or Not Run to Fault/Malfunction if a condition exists.
* A condition in the heated O2 sensor (HO2S) heater control circuits may set a DTC P0300.
Reference Information
Schematic Reference
Engine Controls Schematics (LE9) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Sunshade - Left (DH6)
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
* Powertrain Component Views Powertrain Component Views
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Special Tools
J 38522 - Variable Signal Generator
For equivalent regional tools, refer to Special Tools (Diagnostic Tools) Tools and Equipment.
Circuit/System Verification
1. Engine idling at the normal operating temperature. Verify there is no abnormal engine noise.
• If there is an abnormal engine noise, refer to Symptoms - Engine Mechanical Symptoms - Engine Mechanical.
2. Verify that no other DTCs are set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
3. Observe the scan tool Misfire Current Cyl. 1-4 parameters. The Misfire Current Counters should not be incrementing.
4. 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.
5. 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 Fuel System Diagnosis.
* Contaminated fuel-Refer to Alcohol/Contaminants-in-Fuel Diagnosis Testing and Inspection.
* Exhaust system restrictions
• If you find any of the above conditions, repair as necessary.
2. Ignition OFF, remove the T8 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. Install the J 26792 - HEI Spark Tester to the boot of the appropriate T8 ignition coil and ground.
Note: An erratic or weak spark is considered a no spark condition.
5. Attempt to start the engine and observe the J 26792 - HEI Spark Tester. The spark tester should spark.
• If there is no spark, refer to Electronic Ignition System Diagnosis Electronic Ignition (EI) System Diagnosis for diagnosis of the ignition coil.
6. 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 Testing and Inspection.
* Cracked, worn, incorrectly gapped-Refer to Ignition System Specifications [1][2]Specifications.
• If there is a condition with the spark plug, replace the spark plug.
7. Exchange the suspected spark plug with another cylinder that is operating correctly.
8. Operate the engine under the conditions in which the misfire occurred. Observe the Misfire Current Cyl. 1-4 parameters with a scan tool. The misfire should not follow the spark plug exchange.
• If the misfire follows the spark plug, replace the spark plug.
9. If all conditions test normal, test or inspect for the following:
* A lean or rich Q17 fuel injector-Refer to Fuel Injector Solenoid Coil Test Fuel Injector Solenoid Coil Test.
* An engine mechanical condition-Refer to Symptoms - Engine Mechanical Symptoms - Engine Mechanical.
Repair Instructions
* Ignition Coil Replacement Service and Repair
* Spark Plug Replacement Service and Repair
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 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 Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.