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On Board Diagnosis Logic
NGEC0708
When a misfire occurs, engine speed will fluctuate. If the engine
speed fluctuates enough to cause the CKP sensor signal to vary,
ECM can determine that a misfire is occurring.
Sensor Input Signal to ECM ECM function
Crankshaft position sensor (OBD) 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 dam-
age the three way catalyst (TWC) due to overheating, the MIL
will blink.
When a misfire condition occurs, the ECM monitors the CKP
sensor 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 con-
dition 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 damage the TWC (but will
affect vehicle emissions), the MIL will only light when the mis-
fire is detected on a second trip. During this condition, the ECM
monitors the CKP sensor signal every 1,000 engine revolu-
tions.
A misfire malfunction can be detected on any one cylinder or
on multiple cylinders.
Malfunction is detected when multiple cylinders misfire, No. 1 cyl-
inder misfires, No. 2 cylinder misfires, No. 3 cylinder misfires, No.
4 cylinder misfires, No. 5 cylinder misfires and No. 6 cylinder mis-
fires.
POSSIBLE CAUSE
NGEC0708S01
쐌 Improper spark plug
쐌 Insufficient compression
쐌 Incorrect fuel pressure
쐌 The injector circuit is open or shorted
쐌 Injectors
쐌 Intake air leak
쐌 The ignition secondary circuit is open or shorted
쐌 Lack of fuel
쐌 Drive plate or flywheel
쐌 Heated oxygen sensor 1 (front)
쐌 Incorrect distributor rotor
DTC P0300 - P0306 NO.6-1CYLINDER MISFIRE, MULTIPLE
CYLINDER MISFIRE
VG33E
On Board Diagnosis Logic
EC-927
GI
MA
EM
LC
FE
CL
MT
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
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