Circuit Description

ECM uses signals provided by crankshaft and camshaft position sensors. If engine speed rate has changed enough to equal a preset number, a misfire is detected and MIL is illuminated. If misfire rate is high enough, and driving conditions will cause catalytic converter damage or overheating, MIL blinks when a misfire is occurring. DTC is set when misfiring of random cylinders is detected during any particular 200 or 1000 revolutions. Possible causes are:

• Faulty ignition system.
• Faulty fuel injector(s).
• Improper fuel pressure.
• Faulty engine compression.
• Improper valve clearance.
• Improper valve timing.
• Faulty Mass Airflow (MAF) meter.
• Faulty Engine Coolant Temperature (ECT) sensor.
• Open or short in wiring.
• Poor connector contact at ECM.
• Faulty ECM.