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:

• Ignition System
• Injector(s)
• Fuel Pressure
• EGR System
• Engine Compression
• Valve Clearance
• Valve Timing
• Mass Airflow (MAF) Sensor
• Engine Coolant Temperature (ECT) Sensor
• Open Or Short In Secondary Ignition Wire
• Loose Connector
• ECM