Circuit Description

Misfire: 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. And when the misfire rate equals or exceeds the count indicating that the engine condition has deteriorated, the MIL lights up.

If the misfire rate is high enough and the driving conditions will cause catalyst overheating, the MIL blinks when misfiring occurs.


DTC Detecting Condition

Trouble Area

• Open or short in engine wire

• Connector connection

• Vacuum hose connection

• Ignition system


Misfiring of random cylinders is detected during any particular

• Injector


200 or 1,000 revolutions

• Fuel pressure


For any particular 200 revolutions for the engine, misfiring is

• Manifold absolute pressure sensor


detected which can cause catalyst overheating

• Engine coolant temp. sensor


(This causes MIL to blink)

• Compression pressure

• Valve clearance

• Valve timing


• When the 2 or more codes for a misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates that the misfires were detected and recorded at different times.

• There is a case where the cylinder other than memorized has an accidental fire (the cylinder which is one ahead of fired cylinder), so. at the time of checking all the checking items and if there is no abnormality, check the cylinder which is different from the recorded cylinder as fired.





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