Circuit Description

A misfire is determined by the ECM. The ECM uses signals provided by the crankshaft and Camshaft Position (CMP) 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.

Code is set when misfiring of random cylinders is detected during any particular 200 or 1000 revolutions. Possible causes are:

• Ignition system
• Injector(s)
• Fuel pressure
• EGR system
• Engine compression
• Valve clearance
• Valve timing
• Mass Airflow (MAF) sensor
• Coolant Temperature Sensor (CTS)