Diagnostic Instructions
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. 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 P0306 correspond to cylinders 1 through 6. 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
• | DTC P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, or P0338 is not set. |
• | The engine speed is between 420-7,000 RPM and steady. |
• | The evaporative emissions (EVAP) leak detection is not active. |
• | The delivered torque signal is greater than 10 percent at idle. |
• | The delivered torque signal is between 11-29 percent with the transmission in drive. |
• | The intake air temperature (IAT) is greater than -30°C (-22°F). |
• | The A/C compressor clutch is not changing states. |
• | The torque management is not active. |
• | The antilock brake system/traction control system (ABS/TCS) is not active. |
• | The ECM is not receiving a rough road signal. |
• | The fuel level is greater than 11 percent. |
• | The ECM is not in fuel cut-off or decel fuel cut-off mode. |
• | The throttle angle is steady. |
• | DTCs P0300 through P0306 run continuously when the above conditions exist for at least 1,000 engine revolutions. |
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, P0301, P0302, P0303, P0304, P0305, and P0306 are Type A (MIL flashing) or Type B1 DTCs.
Conditions for Clearing the DTC
DTCs P0300, P0301, P0302, P0303, P0304, P0305, and P0306 are Type A (MIL flashing) or Type B1 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 |
- | A damaged accessory drive component or belt |
• | High resistance in the circuits of the injectors could 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. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Special Tools
J 26792 Spark Tester
For equivalent regional tools, refer to
Special Tools.
Circuit/System Verification
- Engine idling at the normal operating temperature. There should be no abnormal engine noise.
- Verify that DTC P0011, P0014, P0021, P0024, P0201-P0206, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0274, P0276, P0277, P0335, P0336, P0338, P0351-P0356, P2088, P2090, P2092, P2094, P2300, P2301, P2303, P2304,
P2306, P2307, P2309, P2310, P2312, P2313, P2315, or P2316 is not set.
- Observe the scan tool Cylinder 1-6 Current Misfire Counter parameters. The Current Misfire Counters should not increment.
- 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.
- 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
- Verify that the following conditions do not exist:
• | Vacuum hose splits, kinks, and incorrect connections |
• | Crankcase ventilation system for vacuum leaks |
• | Exhaust system restrictions |
⇒ | If you find any of the above conditions, repair as necessary. |
- Ignition OFF, remove the appropriate T8 ignition coil of the misfiring cylinder, but leave the electrical connector connected.
- Inspect the ignition coil boot for the following conditions:
⇒ | If you find any of the above conditions, repair as necessary. |
- Remove the fuel pump fuse from the fuse block.
- Install the
J 26792 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.
- Attempt to start the engine and observe the
J 26792 Spark Tester
. The spark tester should spark.
- 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 |
⇒ | If there is a condition with the spark plug, replace the spark plug. |
- Exchange the suspected spark plug with another cylinder that is operating correctly.
- Engine idling, observe the scan tool Current Misfire Counter parameters. The misfire should not follow the spark plug exchange.
⇒ | If the misfire follows the spark plug, replace the spark plug. |
- If all conditions test normal, test or inspect for the following:
Repair Instructions
Spark Plug Replacement
Repair Verification
- If the customer concern was a flashing malfunction indicator lamp (MIL), refer to
DTC P0420.
- Clear the DTCs with a scan tool.
- Turn OFF the ignition for 30 seconds.
- Start the engine.
- 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.
⇒ | If the DTC fails this ignition, a misfire still exists. |