Description
The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) 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 (TWC) damage. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for catalytic converter damage are preset. DTCs P0301-P0306 correspond to cylinders 1-6. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder sets.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | 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 |
Conditions for Running the DTC
| • | DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, and P0338 are not set. |
| • | The engine speed is between 400-7,000 RPM and steady. |
| • | The delivered torque signal is more than 10 percent at idle. |
| • | The delivered torque signal is between 9-30 percent with the transmission in drive. |
| • | The intake air temperature (IAT) is more than -30°C (-22°F). |
| • | The fuel level is more than 12 percent. |
| • | The torque management is not active. |
| • | The antilock brake system (ABS)/traction control system (TCS) is not active. |
| • | The ECM is not receiving a rough road signal. |
| • | The fuel cut-off is not active, including the traction control, the deceleration, the high vehicle speed, and the high engine speed. |
| • | DTCs P0301 - P0306 run continuously when the above conditions exist for at least 1000 engine revolutions. |
Conditions for Setting the DTC
| • | The ECM detects a crankshaft rotation speed variation indicating a single cylinder misfire rate sufficient to cause emissions levels to exceed mandated standard. |
| • | The condition above exists for more than 4 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the MIL on the second ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail within similar conditions. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
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 |
| • | A misfire DTC could be caused by a camshaft actuator stuck in the full advance or retard position. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Step | Action | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||
2 | Were you sent here from DTC P0300? | Go to Step 3 | Go to DTC P0300 | ||||||||
3 |
Did you find a condition with the ignition coil boot? | Go to Step 12 | Go to Step 4 | ||||||||
4 |
Does the spark tester spark and is the spark consistent? | Go to Step 5 | |||||||||
5 |
Does the spark plug appear to be OK? | Go to Step 9 | Go to Step 6 | ||||||||
6 | Is the spark plug oil or coolant fouled? | Go to Symptoms - Engine Mechanical in Engine Mechanical - 3.6L (LY7) | Go to Step 7 | ||||||||
7 | Is the spark plug gas fouled? | Go to Step 10 | Go to Step 8 | ||||||||
8 | Does the spark plug show any signs of being cracked, worn, or incorrectly gap? | Go to Step 11 | Go to Step 9 | ||||||||
9 |
Did the misfire move with the spark plug? | Go to Step 11 | Go to Step 10 | ||||||||
10 |
Important:
Perform the fuel injector coil test. Refer to Fuel Injector Solenoid Coil Test . Did you find and correct the condition? | Go to Step 13 | Go to Symptoms - Engine Mechanical in Engine Mechanical - 3.6L (LY7) | ||||||||
11 | Replace the spark plug. Refer to Spark Plug Replacement . Did you complete the replacement? | Go to Step 13 | -- | ||||||||
12 | Replace the ignition coil. Refer to Ignition Coil Replacement - Bank 1 and Ignition Coil Replacement - Bank 2 . Did you complete the replacement? | Go to Step 13 | -- | ||||||||
13 | Was the customer's concern that the malfunction indicator lamp (MIL) is flashing? | Go to DTC P0420 | Go to Step 14 | ||||||||
14 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 15 | ||||||||
15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||||||
