Circuit Description

WARNING: This page is about a different car, the 2002 Toyota MR2. However, it is still accessible from the selected car via links, so may be relevant.

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 great 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:

Open or short in wiring.
Poor contact at ECM or component.
Disconnect, blocked or damaged vacuum hose(s).
Ignition system malfunction.
Defective fuel injector(s).
Improper fuel pressure.
Defective Mass Airflow (MAF) meter.
Defective Engine Coolant Temperature (ECT) sensor.
Improper engine compression.
Improper valve clearance.
Improper valve timing.
Defective ECM.