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On Board Diagnosis Logic
NFEC0929
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 (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 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 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 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.
DTC No.
Trouble diagnosis
name
DTC Detecting Condition Possible Cause
P0300
0300
Multiple cylinder mis-
fire detected
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.
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
I Incorrect PCV hose connection
P0301
0301
No. 1 cylinder misfire
detected
P0302
0302
No. 2 cylinder misfire
detected
P0303
0303
No. 3 cylinder misfire
detected
P0304
0304
No. 4 cylinder misfire
detected
P0305
0305
No. 5 cylinder misfire
detected
P0306
0306
No. 6 cylinder misfire
detected
GI
MA
EM
LC
FE
CL
MT
AT
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0300 - P0306 MULTIPLE CYLINDER MISFIRE, NO.1-6CYLINDER
MISFIRE
On Board Diagnosis Logic
EC-317
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