Description
The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor 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 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 P0101, P0102, P0103, P0106, P0107, P0108, P0121, P0122, P0123, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0274, P0276, P0277, P0335, P0336, P0337, P0341, P0342, P1320, and P1321 are not set. |
| • | The engine speed is between 500-6,500 RPM and steady. |
| • | The engine coolant temperature (ECT) is more than -7.5°C (18.5°F). |
| • | The barometric pressure (BARO) is more than 74.5 kPa. |
| • | The ignition 1 voltage is more than 11 volts. |
| • | The throttle angle and mass air flow (MAF) are steady. |
| • | 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 ECM is not in fuel cut-off or decel fuel cut-off mode. |
| • | The transmission is not changing gears. |
| • | The A/C clutch is not changing states. |
| • | DTCs P0301-P0306 runs continuously when the above conditions are met. |
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.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | 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 |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Step | Action | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | |||||||||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | Go to Step 2 | |||||||||
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-2.5L (LBK) | 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 |
Does the same misfire DTC set? | Go to Step 10 | Go to Step 11 | ||||||||
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-2.5L (LBK) | ||||||||
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 . 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 or P0430 | 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? | System OK | |||||||||
