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-P0306 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 P0121, P0122, P0123, P0222, P0223, P0335, P0341, P0342, P0343, P0440, P0443, P0444, or P0445 are not set. |
| • | The engine speed is between 520-6,520 RPM. |
| • | The torque management is not active. |
| • | 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 has been running for longer than 5 seconds. |
| • | The intake air temperature (IAT) is more than -30°C (-22°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 report 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 current 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 | 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 Step 6 |
6 |
Does the spark tester spark? | -- | Go to Step 8 | Go to Step 7 |
7 | 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 | Go to Step 12 |
8 |
Does the spark plug appear to be OK? | -- | Go to Step 9 | Go to Step 10 |
9 |
Did the misfire move with the spark plug? | -- | Go to Step 14 | Go to Symptoms - Engine Mechanical in Engine Mechanical |
10 | Is the spark plug oil or coolant fouled? | -- | Go to Symptoms - Engine Mechanical in Engine Mechanical | Go to Step 11 |
11 | Does the spark plug show any signs of being cracked, worn gas fouled, or improperly gapped? | -- | Go to Step 13 | Go to Symptoms - Engine Mechanical in Engine Mechanical |
12 | Perform the ignition control (IC) system diagnosis. Refer to Electronic Ignition (EI) System Diagnosis . Did you find and correct the condition? | -- | Go to Step 15 | -- |
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 15 | -- |
15 | Was the customer concern the malfunction indicator lamp (MIL) flashing? | -- | Go to Step 16 | Go to Step 17 |
16 |
Does the DTC run and pass? | 2,500 RPM | Go to Step 18 | Go to DTC P0421 or P0431 |
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 |
