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: Description

When a misfire occurs in the engine, hydrocarbons (HC) enter the exhaust gas in high concentrations. If this HC concentration is high enough, there could be an increase in exhaust emissions levels. High concentrations of HC can also increase the temperature of the catalyst, possibly damaging the catalyst. To prevent this 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 blink the MIL. For monitoring misfire, 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 increments when crankshaft rotation speed variations exceed threshold values.

If the misfiring rate exceeds the threshold value and could cause emissions deterioration, the ECM illuminates the MIL.

DTC TROUBLE DETECTION CONDITION CHART

DTC No.	DTC Detection Condition	Trouble Area
P0300	Misfiring of random cylinders is detected during any particular 200 or 1,000 revolutions trip detection logic: MIL blinks trip detection logic: MIL illuminates	Open or short in engine wire harness Connector connection Vacuum hose connection Ignition system Injector Fuel pressure Mass air flow meter Engine coolant temperature sensor Compression pressure Valve clearance Valve timing PCV hose connection PCV hose ECM
P0301 P0302 P0303 P0304	For any particular 200 revolutions of engine, misfiring is detected which can cause catalyst overheating (This causes MIL to blink) For any particular 1,000 revolutions of engine, misfiring is detected which causes a deterioration in emissions (2 trip detection logic)	Open or short in engine wire harness Connector connection Vacuum hose connection Ignition system Injector Fuel pressure Mass air flow meter Engine coolant temperature sensor Compression pressure Valve clearance Valve timing PCV hose connection PCV hose ECM

NOTE: When several codes for a misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates that the misfires have been detected and recorded at different times.

Reference: Inspection using oscilloscope

With the engine idling, check the waveform between terminals #10 to #40 and E01 of the ECM connectors.

HINT:

The correct waveform is as shown.

Fig 1: Injector Signal Waveform