DTC P0300-P0306: RANDOM MISFIRE DETECTED Lexus ES XV20

Note. When 2 or more codes for a misfiring cylinder are recorded repeatedly, but DTC P0300 is not recorded, it indicates that misfires were detected and stored into ECM memory at different times.

Circuit Description

A misfire is determined by the ECM. The ECM uses signals provided by the crankshaft and camshaft position sensors. If the engine speed rate has changed enough to equal a preset number, a misfire is detected and the MIL is illuminated. If the misfire rate is high enough, and driving conditions will cause catalytic converter damage or overheating, the MIL blinks when a misfire is occurring. DTC P0300 is set when misfiring of random cylinders is detected during any particular 200 or 1000 revolutions. DTC P0301-P0306 are set when during any particular 200 revolutions of engine, misfiring is detected which can cause catalytic converter overheating and/or damage. DTC P0301-P0306 will also set when during any particular 1000 revolutions of engine, misfiring is detected which can cause a deterioration in emission levels. DTC P0300-P0306 may also set if vehicle has run out of fuel. Possible causes are

1. Ignition System
2. Injector(s)
3. Fuel Pressure
4. EGR System
5. Engine Compression
6. Valve Clearance
7. Valve Timing
8. Mass Airflow (MAF) Sensor
9. Engine Coolant Temperature (ECT) Sensor
10. Open Or Short In Secondary Ignition Wire
11. Loose Connector
12. ECM