Circuit Description
WARNING: This page is about a different car, the 2003 Toyota 4Runner. However, it is still accessible from the selected car via links, so may be relevant.
The ECM uses the crankshaft position sensor and camshaft position sensor to monitor changes in the crankshaft rotation for each cylinder. The ECM counts the number of times the engine speed change rate indicates that misfire has occurred. When the misfire rate equals to or exceeds the count of indicating that the engine condition has deteriorated, the MIL is illuminated. If the misfire rate is high enough and the driving conditions will cause the catalyst to overheat, the MIL blinks when misfiring occurs.