• Perform the Diagnostic System Check prior to using this diagnostic procedure:Diagnostic System Check - Vehicle
• Review the description of Strategy Based Diagnosis:Strategy Based Diagnosis
• An overview of each diagnostic category can be found here:Diagnostic Procedure Instructions

For an overview of the component/system, refer to:

• Electronic Ignition System Description
• Fuel System Description

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. The engine control module (ECM) is able to detect these variations by closely monitoring the crankshaft position sensor signal. The signals of the camshaft position sensors are used to determine which cylinder is misfiring. If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 sets. Under certain driving conditions, a misfire rate can be high enough to cause the catalytic converter to overheat, possibly damaging the converter. The malfunction indicator lamp (MIL) flashes when catalyst damaging misfire conditions are present and DTC P0300 is set.

• DTC P0010, P0011, P0013, P0014, P0016, P0017, 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, P0365, P0366, P0601, P0604, P0606, P0651, P16A0, P16A1, P16A2, P16F3, P2101, P2135, P2227, P2228, P2229, P2230 = Not set
• Crankshaft/Camshaft Sensors=Synchronized
• Engine Coolant Temperature=−12 to 127°C (24.4 to 261°F)
• Engine Load=20%
• Engine Speed=Greater than 900 RPM
• {If DTC P0315 is set}Engine Speed=Greater than 1,000 RPM
• Fuel Cut-Off System=Inactive
• Fuel level=Greater than 11%
• Rough Road Signal=Not Detected
• System Voltage=9 to 32 V

Frequency the DTC runs=Continuously—After the running conditions are met

The control module K20 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.

The control module K20 detects a crankshaft rotation speed variation indicating a single cylinder misfire rate sufficient to cause emissions levels to exceed mandated standards.

DTCs listed in the DTC Descriptor category=Type B DTC

Malfunction Indicator Lamp (MIL)=Flashing—During catalyst damaging misfire.

DTCs listed in the DTC Descriptor category=Type B DTC

• { If equipped }Command the Cylinder Deactivation system On with a scan tool, then observe the misfire counters when commanding the system Off. If the misfire counters are incrementing, inspect for a sticking valve lifter.
• DTC P0300–P0304 may set when there is a condition with the component circuits:B52 Heated Oxygen Sensor
• High resistance in the circuits of the component may set DTC P0300–P0304 without setting the DTC for the component:Q17 Fuel Injector
• If the condition is intermittent, wiggle the related wiring harnesses and connectors, with the ignition/vehicle on or engine running, while monitoring the scan tool circuit status parameters for the component. The parameters will display if there is a condition with the circuit or a connection.
• The following conditions could cause DTC P0300–P0304 to set:
• Accessory drive bracket—Defective/Loose/Visible Damage
• Belt Driven Device—Defective/Loose/Visible Damage
• Brake Rotor—Excessive runout
• Drive Belt—Defective/Loose/Visible Damage
• Drive Shaft—Excessive runout
• During certain road conditions:Rough
• Transmission—Incorrect Operation
• Tire and wheel assemblies which exhibit excessive runout can produce vibrations even if the assemblies are balanced.

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Control Module References

J-26792 - Ignition Spark Tester

Equivalent regional tools:Special Tools

1. Engine»Running
2. Verify there is no abnormal noise from the component:Engine
• If an abnormal noise is present

  Refer to:Symptoms - Engine Mechanical

• If no abnormal noise is present
3. Perform the scan tool learn/reset function:Crankshaft Position Variation Learn
4. Verify there are no DTCs set related to the following component/system:
• B23 Camshaft Position Sensor
• B26 Crankshaft Position Sensor
• B52 Heated Oxygen Sensor
• Q17 Fuel Injector
• T8 Ignition Coil
• Fuel System
• Ignition System
• Mechanical Condition
• If a related DTC is set

  Refer to:Diagnostic Trouble Code (DTC) List - Vehicle

• If a related DTC is not set
5. Verify the scan tool parameter:Cylinder 1–4 Current Misfire Counter=Does not Increment
• If the parameter value increments

  Refer to: Circuit/System Testing

• If the parameter value does not increment
6. Perform the scan tool control function:Cylinder Power Balance»Enable

   Verify the engine speed or sound changes the same way when turning off each fuel injector.

• If the engine sound does not change the same way for one or more cylinders

  Refer to: Circuit/System Testing

• If the engine sound changes the same way for all cylinders
7. Verify the scan tool parameter:Cylinder 1–4 Current Misfire Counter=Does not Increment

   Perform the action while monitoring the parameter:

• Wiggle the harness and connector(s):K20 Engine Control Module
• Wiggle the harness and connector(s):Q17 Fuel Injector
• Wiggle the harness and connector(s):T8 Ignition Coil
• Wiggle the component:Vacuum Hoses
• If the parameter value increments

  Repair or replace as necessary

• If the parameter value does not increment
8. 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.

   Verify the DTC does not set.

• If the DTC sets

  Refer to: Circuit/System Testing

• If the DTC does not set
9. All OK.

1. Verify the following conditions do not exist:
• Engine—Vacuum leak
• Exhaust System—Leaking/Missing components/Restricted»Refer to:Symptoms - Engine Exhaust
• Fuel—Contaminated/Dirty/Fill Level=Low»Refer to:Alcohol/Contaminants-in-Fuel Diagnosis
• Fuel Pressure—High/Low»Refer to:Fuel System Diagnosis
• Positive Crankcase Ventilation System—Leaking/Incorrect connection/Restricted
• Vacuum Hoses—Kinked/Leaking/Incorrect connection/Restricted
• If a condition exists

  Repair or replace as necessary

• If no conditions exist
2. Ignition/Vehicle » Off
3. Remove the appropriate component:T8 Ignition Coil—Leave the electrical connector connected.
4. Verify a condition does not exist with the component:Spark Plug Boot—Carbon Tracking/Fluid intrusion/Visible Damage
• If a condition exists

  Repair or replace as necessary

• If no condition exists
5. Install»J-26792 - Ignition Spark Tester@T8 Ignition Coil&Ground
6. Engine»Running

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

7. Verify there is spark at the tool.
• If there is no spark

  Refer to:Electronic Ignition System Diagnosis

• If there is spark
8. Ignition/Vehicle » Off
9. Remove the appropriate component:Spark Plug
10. Verify the component specifications are correct:Spark Plug—Gap/Heat Range/Torque»Refer to:Ignition System Specifications
• If not correct

  Repair or replace as necessary

• If correct
11. Verify a condition does not exist with the component:Spark Plug—Carbon Tracking/Fouled/Visible Damage
• If a condition exists

  Repair or replace as necessary

• If no condition exists
12. Swap the two components:Spark Plug—The original component that set the DTC&Another known good component from the vehicle
13. Engine»Running
14. Verify the scan tool parameter:Cylinder 1–4 Current Misfire Counter=Increments—At the original component location the DTC set.
• If the parameter value does not increment

  Replace the component:Spark Plug—The original component that set the DTC

• If the parameter value increments
15. Perform the following procedure/test:Fuel Injector Balance»Refer to:Fuel Injector Diagnosis

    Verify the procedure/test passes.

• If the procedure/test does not pass

  Replace the component that failed the test:Q17 Fuel Injector

• If the procedure/test passes
16. Verify the condition does not exist:An engine mechanical condition»Refer to:Symptoms - Engine Mechanical
• If a condition exists

  Repair or replace as necessary

• If no condition exists
17. All OK.

Perform the Diagnostic Repair Verification after completing the repair:Diagnostic Repair Verification

After any repair, operate the vehicle within the Conditions for Running the DTC P0420 to verify the performance of the component:Catalytic Converter»Refer to:DTC P0420

• Ignition Coil Replacement
• Gas Engine Ignition Spark Plug Replacement