P0300

DTC P0300

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 present. DTCs P0301-P0308 correspond to cylinders 1-8. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will set.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0300 Engine Misfire Detected

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 system (ABS) 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).
- DTC P0300 runs continuously once the above conditions are met.

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

DIAGNOSTIC AIDS
- Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration:
- Thickness variation of the brake rotors-Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes. Symptoms - Hydraulic Brakes
- The drive shaft not balanced-Refer to Vibration Analysis - Driveline in Vibration Diagnosis and Correction. Component Tests and General Diagnostics
- Worn or damaged accessory drive belt-Refer to Symptoms - Engine. Symptom Related Diagnostic Procedures
- There may be more or less cylinders actually misfiring than indicated by the scan tool.
- If there are multiple misfires on only one bank, inspect the fuel injector and ignition coil, power and ground circuits for that bank.

TEST DESCRIPTION

Step 1 - Step 7:

Step 8 - Step 19:

The number below refers to the step number on the diagnostic table.
2. If the actual CKP variation values are not within the learned values, the misfire counters may increment.