By using a high frequency crankshaft position signal, the ECM can closely monitor crankshaft speed variations during individual cylinder power strokes. When an engine is firing cleanly on all cylinders, the crankshaft speeds up with each power stroke. When misfire occurs, crankshaft speed increase is effected for that cylinder.
Toyota OBD-II engines use a 36 minus 2 tooth Ne sensor which directly measures crankshaft speed and position. This information is processed by the ECM to determine if misfire occurs, which cylinder it is occurring in, and the degree of misfire.
When a misfire of any significance is detected, a DTC is stored and the engine speed, load and warm-up status at the time of misfire will be stored. Additionally, the vehicle operator will be alerted to the condition by a rapidly flashing MIL during periods when significant misfire is occurring.
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