System 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-P0308 correspond to cylinders 1-6. 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
| • | DTCs P0102, P0103, P0315, P0335, P0336, P0365, P0366, or P0390 are not set. |
| • | The engine speed is between 500-6,496 RPM. |
| • | The engine load is more than 0 percent. |
| • | The torque management is not active. |
| • | The fuel level is more than 10.5 liters (3 gallons). |
| • | The antilock brake (ABS) system is not active. |
| • | The ECM is not receiving a rough road signal. |
| • | The ECM is not in fuel shut-off or decel mode. |
| • | The engine coolant temperature (ECT) is more than -7.5°C (18.5°F). |
Conditions for Setting the DTC
The ECM is detecting a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standards.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive 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 ECM turns OFF the MIL after 3 consecutive drive trips that the diagnostic runs and does not fail within the same conditions that the DTC last failed. |
| • | A History DTC clears after 40 consecutive warm-up cycles if no failures are reported by this diagnostic or any other emission related diagnostic. |
| • | The DTC can be cleared with a scan tool |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 |
Are any of the misfire counters incrementing? | -- | Go to Step 3 | Go to Intermittent Conditions |
3 | Are any DTCs other than DTC P0300 set? | -- | Go to Step 4 | |
4 | Can any abnormal engine noise be heard? | -- | Go to Symptoms - Engine Mechanical in Engine Mechanical | Go to Step 5 |
5 |
Did the spark tester spark? | -- | Go to Step 7 | Go to Step 6 |
6 | Inspect the affected cylinder spark plug boot for a missing or damaged ignition coil spring. Did you find and correct the condition? | -- | Go to Step 15 | |
7 |
Does the spark plug appear to be OK? | -- | Go to Step 8 | Go to Step 9 |
8 |
Did the misfire move with the spark plug? | -- | Go to Step 14 | Go to Step 12 |
9 | Is the spark plug oil or coolant fouled? | -- | Go to Symptoms - Engine Mechanical in Engine Mechanical | Go to Step 10 |
10 | Is the spark plug gas fouled? | -- | Go to Step 12 | Go to Step 11 |
11 | Does the spark plug show any signs of being cracked, worn, or improperly gapped? | -- | Go to Step 13 | Go to Step 12 |
12 | Perform the fuel injector coil test. Refer to Fuel Injector Solenoid Coil Test . Did you find and correct the condition? | -- | Go to Step 15 | Go to Symptoms - Engine Mechanical in Engine Mechanical |
13 | Replace or gap the spark plug. Refer to Spark Plug Replacement . If an improper gap is found, be sure to gap the spark plugs using a wire type gage. Did you complete the action? | -- | Go to Step 15 | -- |
14 | Replace the faulty spark plug. Refer to Spark Plug Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- |
15 | Was the customer concern the MIL flashing? | -- | Go to Step 16 | Go to Step 17 |
16 |
Does the DTC run and pass? | 2,500 RPM | Go to Step 17 | Go to DTC P0420 or P0430 |
17 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 18 |
18 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK |
