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 P0301Cylinder 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, or 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 with the transmission in neutral. |
| • | The delivered torque signal is between 10-30 percent with the transmission in drive. |
| • | The intake air temperature (IAT) is more than -30°C (-22°F). |
| • | The engine run time is more than 45 seconds. |
| • | 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, P0302, P0303, P0304, P0305, and 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 standards. |
| • | The condition exists for more than 4 seconds. |
Action Taken When the DTC Sets
| • | The MIL flashes any time the misfire rate is sufficient to cause damage to the catalyst. |
| • | 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 malfunction indicator lamp (MIL) at the beginning of the fourth ignition cycle, after 3 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 and related Freeze Frame data clears after 40 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. Check for the following possible sources: |
| - | Tire or wheel out of round or balance |
| - | Variable thickness brake rotor or drum |
| - | Drive shaft not balanced |
| - | Certain rough road conditions |
| - | Damaged accessory drive belt |
| • | 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 | |||||||||
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 |
Important: The fuel pump fuse is located under the right rear seat. The carpet must be lifted up to access the rear fuse block. 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 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 | |||||||||
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 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 | |||||||||
