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 and/or add fuel. The ECM will re-enable the fuel injector after 3 crankshaft revolutions (6 for manual transmission vehicles) to determine if a misfire is still present and either disable for 3 crankshaft revolutions (6 for manual transmission vehicles) again or stay enabled, depending on whether the misfire is still present.
Conditions for Running the DTC
* DTC 0010, P0011, P0013, P0014, P0016, P0017, P0018, P0019, P0020, P0021, P0023, P0024, P0068, P00C8, P00C9, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0117, P0118, P0119, P0122, P0123, P0191, P0192, P0193, P0222, P0223, P0335, P0336, P0340, P0341, P0345, P0346, P0365, P0366, P0390, P0391, P0601, P0604, P0606, P0651, P16A0, P16A1, P16A2, P16F3, P2101, P2135, P2227, P2228, P2229, or P2230 is not set.
AND
* DTC P0806, P0807, or P0808 is not set; with manual transmission.
* The engine speed is greater than 1,400 RPM.
OR
* The engine speed is less than 1,000 RPM and DTC P0315 is set.
* The engine coolant temperature (ECT) is between -7 and +125°C (19 and 257°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°C and 125°C (69 and 257°F).
* The ignition voltage is between 9 and 32 V.
* The vehicle is not in a decel condition.
* The ECM is not detecting 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.
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 or a misfire rate high enough to cause catalyst damage.
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 may disable up to two fuel injector's of the misfiring cylinder's when a catalyst damaging level of misfire is present. And will flash the malfunction indicator lamp (MIL).
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
- Cracked Spark Plug Insulators
- Broken or weak valve spring
- A damaged or defective accessory drive component or belt; remove the belt and safely operate the engine to evaluate if misfire counts go away.
* 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 [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Sunshade - Left
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 Left Rear of Engine Components
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 26792 - HEI Spark Tester
For equivalent regional tools, refer to Special Tools Tools and Equipment.
Circuit/System Verification
Note: Before starting vehicle, review freeze frame data to determine if misfire sets during cold start or warmed up operation. If the vehicle has a cold start problem and the vehicle is started, the vehicle will require a soak of many hours before next attempt to operate the vehicle within the fail conditions.
1. Engine idling at the normal operating temperature.
2. Verify there is no abnormal engine noise.
• If there is an abnormal engine noise
Refer to Symptoms - Engine Mechanical (LCV) Symptoms - Engine MechanicalSymptoms - Engine Mechanical (LTG) Symptoms - Engine Mechanical.
• If there is no abnormal engine noise
3. Verify no DTCs other than P0300-P0304 are set.
• If any DTCs other than P0300-P0304 are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
• If only DTCs P0300-P0304 are set
Refer to Circuit/System Testing.
• If no DTCs are set
4. Verify the scan tool Cylinder 1-4 Current Misfire Counter are not incrementing.
• If a Counter is incrementing
Refer to Circuit/System Testing.
• If a Counter is not incrementing
5. Engine idling.
6. Verify the engine speed changes when performing the Cylinder Power Balance Test with a scan tool.
• If engine speed does not change
Refer to Circuit/System Testing.
• If the engine speed changes
7. 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 data.
8. Verify the DTCs are not set.
• If any of the DTCs set
Refer to Circuit/System Testing.
• If none of the DTCs set
9. All OK.
Circuit/System Testing
1. Perform the Crankshaft Position System Variation Learn Testing and Inspection procedure. The scan tool should display Learned Successful.
• If the Crankshaft Position System Variation Learn Procedure cannot be performed successfully, inspect for the following conditions and repair as necessary:
* Worn crankshaft main bearings
* A damaged or misaligned reluctor wheel
* Excessive crankshaft runout
* A damaged crankshaft-Refer to Crankshaft Balancer Cleaning and Inspection Crankshaft Balancer Cleaning and Inspection.
* Interference in the signal circuit of the crankshaft position sensor
* The ignition switch is in the ON position until there is insufficient system voltage.
* An ECM power disconnect with the ignition ON that may have erased the crankshaft position system variation values and set DTC P0315
* Debris between the crankshaft position sensor and the reluctor wheel
• If a condition exists
Repair or replace as necessary.
• If no conditions exist
2. Verify the Learn Procedure is successful.
• If the engine control module is unable to complete the learn procedure, replace the K20 Engine Control Module.
3. 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.
• If a condition exists
Repair or replace as necessary.
• If no conditions exist
4. Ignition OFF, remove the T8 Ignition Coil of the misfiring cylinder, but leave the electrical connector connected.
5. Verify none of the conditions listed below exist with the boot of the T8 Ignition Coil:
* Holes
* Tears
* Carbon tracking
* Oil contamination
* Water intrusion
• If a condition exists
Repair or replace as necessary.
• If no conditions exist
Note: An erratic or weak spark is considered a no spark condition.
6. Verify the J 26792 (EL 26792) - HEI Spark Tester sparks while cranking or starting the engine.
• If there is no spark
Refer to Electronic Ignition System Diagnosis Electronic Ignition (EI) System Diagnosis for diagnosis of the ignition coil.
• If there is spark
7. Ignition OFF, remove the spark plug from the misfiring cylinder.
8. Exchange the suspected spark plug with another cylinder that is operating correctly.
9. Engine idling.
10. Verify the scan tool Cylinder 1-4 Current Misfire Counter parameter does not increment on the spark plug coil it was removed from.
• If the misfire does follow the spark plug exchange
Replace the spark plug.
• If the misfire does not follow the spark plug exchange
11. If all conditions test normal, test or inspect for the conditions listed below:
* A lean or rich Q17 Fuel Injector-Refer to Fuel Injector Balance Test Fuel Injector Balance Test.
* An engine mechanical condition-Refer to Symptoms - Engine Mechanical (LCV) Symptoms - Engine MechanicalSymptoms - Engine Mechanical (LTG) 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. 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. Engine idling, observe the Misfire Current Cyl. 1-4 parameters with a scan tool. The misfire counter parameters should not be incrementing.
• If the misfire counter parameters are incrementing, a misfire still exists.
7. 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 (LCV) P0420DTC P0420 (LTG) P0420.