The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensor and the ignition control (IC) module in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way catalytic converter (TWC) to overheat under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the PCM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.
• | DTCs P0107, P0112, P0113, P0117, P0118, P0120, P0121, P0125, P0131, P0132, P0133, P0134, P0171, P0172, P0220, P0336, P0502, P0506, P0507, P0601, P1133, P1621, P2135 are not set. |
• | The engine speed is between 469-6,400 RPM. |
• | The ignition voltage is between 9-17 volts. |
• | The engine coolant temperature (ECT) is between -7 and +123°C (20-254°F). |
• | The engine has been running for more than 5 seconds. |
• | The throttle position (TP) has not increased more than 8 percent in 1 second. |
• | The TP has not decreased more than 1.5 percent in 1 second. |
The PCM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards.
• | 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. |
• | 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. |
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||||
Important: You must perform the crankshaft position (CKP) system variation learn procedure before proceeding with this diagnostic table. Refer to Crankshaft Position System Variation Learn .
Are any of the Misfire Current counters incrementing? | -- | Go to Step 3 | Go to Intermittent Conditions | |||||||||||
3 | Are any other DTCs 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 |
Is the indicated value more than the typical value? | -- | Go to DTC P0108 | Go to Step 6 | ||||||||||
6 | Inspect the following components:
Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 7 | ||||||||||
7 |
Important: Not grounding the IC module housing may cause an erratic spark. Does the spark tester spark on all cylinders? | -- | Go to Step 8 | |||||||||||
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 16 | Go to Step 13 | ||||||||||
10 | Is the spark plug oil or coolant fouled? | -- | Go to Symptoms - Engine Mechanical in Engine Mechanical | Go to Step 11 | ||||||||||
11 | Is the spark plug gas fouled? | -- | Go to Step 14 | Go to Step 12 | ||||||||||
12 | Did the spark plug show any signs of being cracked, worn, or improperly gapped? | -- | Go to Step 15 | Go to Step 13 | ||||||||||
13 | Perform the fuel injector coil test. Refer to Fuel Injector Solenoid Coil Test . Did you find and correct the condition? | -- | Go to Step 17 | Go to Symptoms - Engine Mechanical in Engine Mechanical | ||||||||||
14 | Perform the fuel system diagnosis. Refer to Fuel System Diagnosis . Did you find and correct the condition? | -- | Go to Step 17 | Go to Symptoms - Engine Mechanical in Engine Mechanical | ||||||||||
15 | Replace or gap the spark plug. Refer to Spark Plug Replacement . Did you complete the action? | -- | Go to Step 17 | -- | ||||||||||
16 | Replace the faulty spark plug. Refer to Spark Plug Replacement . Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||||||
17 | Was the customer concern the MIL flashing? | -- | Go to Step 18 | Go to Step 19 | ||||||||||
18 |
Does the DTC run and pass? | 2,500 RPM | Go to Step 19 | Go to DTC P0420 | ||||||||||
19 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 20 | ||||||||||
20 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK |