Test Description

The numbers below refer to the step numbers on the diagnostic table.

2: This step determines if there is a current condition.
4: If the Misfire Current Counters are incrementing, but the engine is NOT misfiring, this indicates a mechanical condition. For example, an accessory drive belt could cause this condition.

DTC P0300

Step	Action	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	IMPORTANT: The engine may only misfire when the engine is under a load. An engine load may be necessary to verify the condition. Start the engine. Allow the engine to reach operating temperature. Monitor the Misfire Current Cyl. 1-6 Counter parameters with a scan tool. Are any of the Misfire Current Counters incrementing?	Go to Step 4	Go to Step 3
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?	Go to Step 4	Go to Diagnostic Aids
4	Is the engine misfiring?	Go to Step 5	Go to Symptoms - Engine Mechanical
5	Observe the DTC Info with a scan tool. Is DTC P0011, P0014, P0021, P0024, P0201-P0206, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0274, P0276, P0277, P0335, P0336, P0338, P0351-P0356, P2088, P2090, P2092, P2094, P2095, P2300, P2301, P2303, P2304, P2306, P2307, P2309, P2310, P2312, P2313, P2315, or P2316 also set?	Go to Diagnostic Trouble Code (DTC) List - Vehicle	Go to Step 6
6	Is there an engine mechanical noise?	Go to Symptoms - Engine Mechanical	Go to Step 7
7	Is there more than one cylinder specific misfire DTC set?	Go to Step 8	Go to DTC P0301-P0306
8	Is there any HO2S DTCs set?	Go to Diagnostic Trouble Code (DTC) List - Vehicle	Go to Step 9
9	Inspect or test for the following conditions: Inspect the vacuum hoses for splits, kinks, and proper connections. Inspect the throttle body and the intake manifold for vacuum leaks. Inspect the crankcase ventilation valve and/or system for any vacuum leaks. Test for the correct fuel pressure. Refer to Fuel System Diagnosis . Inspect the fuel system for any restrictions, leaks or fuel contamination. Refer to Fuel System Diagnosis or Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/Special Tool) . Inspect for fouled or damaged spark plugs. Determine what caused the spark plugs to foul. Refer to Spark Plug Inspection . Inspect the exhaust system for restrictions. Refer to Restricted Exhaust . Inspect the engine control grounds for being clean, tight, and in the correct location. Inspect for a camshaft actuator stuck in the full advance or retard position. Repair as necessary. Did you find and correct the condition?	Go to Step 10	Go to Symptoms - Engine Mechanical
10	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. If the customer concern was the MIL is flashing, operate the vehicle within the Conditions for Running the DTC P0420 . Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?	Go to Step 2	Go to Step 11
11	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	Go to Diagnostic Trouble Code (DTC) List - Vehicle	System OK