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On Board Diagnosis Logic
NHEC0182
If a misfire occurs, the engine speed will fluctuate. If the fluctuation is detected by the crankshaft position sen-
sor (POS), the misfire is diagnosed.
Sensor Input Signal to ECM ECM function
Crankshaft position sensor (POS) Engine speed On board diagnosis of misfire
The misfire detection logic consists of the following two conditions.
1. One Trip Detection Logic (Three Way Catalyst Damage)
On the first trip that a misfire condition occurs that can damage the three way catalyst (TWC) due to
overheating, the MIL will blink.
When a misfire condition occurs, the ECM monitors the crankshaft position sensor (POS) signal every 200
engine revolutions for a change.
When the misfire condition decreases to a level that will not damage the TWC, the MIL will turn off.
If another misfire condition occurs that can damage the TWC on a second trip, the MIL will blink.
When the misfire condition decreases to a level that will not damage the TWC, the MIL will remain on.
If another misfire condition occurs that can damage the TWC, the MIL will begin to blink again.
2. Two Trip Detection Logic (Exhaust quality deterioration)
For misfire conditions that will not cause damage to the TWC (but will affect vehicle emissions), the MIL
will only light when the misfire is detected on a second trip. During this condition, the ECM monitors the
crankshaft positon sensor (POS) signal every 1,000 engine revolutions.
A misfire malfunction can be detected on any one cylinder or on multiple cylinders.
Malfunction is detected when multiple cylinders misfire, No. 1 cylinder misfires, No. 2 cylinder misfires, No. 3
cylinder misfires, No. 4 cylinder misfires, No. 5 cylinder misfires and No. 6 cylinder misfires.
Possible Cause
NHEC0490
I Improper spark plug
I Insufficient compression
I Incorrect fuel pressure
I The injector circuit is open or shorted
I Injectors
I Intake air leak
I The ignition secondary circuit is open or shorted
I Lack of fuel
I Drive plate or flywheel
I Heated oxygen sensor 1 (front)
DTC P0300 - P0306 NO.6-1CYLINDER MISFIRE, MULTIPLE CYLINDER
MISFIRE
On Board Diagnosis Logic
EC-330
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