DTC P0300 Random / Multiple Cylinder Misfire Detected; DTC P0301 Cylinder 1 Misfire Detected; DTC P0302 Cylinder 2 Misfire Detected; DTC P0303 Cylinder 3 Misfire Detected; DTC P0304 Cylinder 4 Misfire Detected; DTC P0305 Cylinder 5 Misfire Detected; DTC P0306 Cylinder 6 Misfire Detected; DTC P0307 Cylinder 7 Misfire Detected; DTC P0308 Cylinder 8 Misfire Detected: Description

Fig 1: Identifying Camshaft Position Sensor

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When a misfire occurs in the engine, hydrocarbons (HC) enter the exhaust in high concentrations. If the HC concentration is too high, exhaust emission levels may increase. High concentrations of HC can also cause the temperature of the catalyst to increase, possibly damaging the catalyst. To prevent the increase in emissions and limit the possibility of thermal damage, the ECM monitors the misfire rate. When the temperature of the catalyst reaches a point of thermal degradation, the ECM will begin flashing the MIL. For monitoring misfires, the ECM uses both the camshaft position sensor and the crankshaft position sensor. The camshaft position sensor is used to identify misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed. The misfire counter records how many times the crankshaft rotation speed variations exceed threshold values.

If the misfiring rate exceeds the threshold value and could cause emissions to deteriorate, the ECM illuminates the MIL and sets a DTC.

DIAGNOSTIC TROUBLE CODE CHART

DTC No.	DTC Detection Condition	Trouble Area
P0300	Misfiring of random cylinder is detected	Ignition coil Fuel injector Fuel pressure Compression pressure Valve timing Valve clearance Vacuum hose PCV hose Air induction system Exhaust system ECM
P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308	Misfiring of each cylinder is detected	Same as DTC No. P0300

HINT:

In some cases, several DTCs for misfired cylinders (DTCs P0301 to P0308) are recorded but the random/ multiple cylinder misfire DTC (P0300) is not recorded. This is an indication that the misfires were detected and recorded at different times. Random misfire codes are recorded only when several misfires occur at the same time.

Reference: Inspection using an oscilloscope.

With the engine idling, check the waveform between terminals #1 to #8 and E1 of the ECM connectors. The correct waveform is as shown.

Fig 2: Identifying Injector Signal Waveform