Subaru IMPREZA GD 2007 Series Manual page 2169

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Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
4. DIAGNOSTIC METHOD
(A)
(B)
(A) Engine control module (ECM)
When a misfire occurs, the engine speed will decreased and the crankshaft position speed will change. Cal-
culate the interval difference value (diagnostic value) from crankshaft position speed by the following formu-
la, and judge whether a misfire is occurring or not comparing the calculated result with judgment value.
Counting the number of misfires. If the misfire ratio is higher during 1,000 revs. or 200 revs., Judge corre-
sponding cylinders as NG.
Diagnosis value cal-
→
culation (Calculated
from angle speed)
(B) Diagnosis circuit
Misfire detection at every
→
ignition (Comparing the
diagnosis value with the
judgement value)
• 180° Interval Difference
Method
• 360° Interval Difference
Method
• 720° Interval Difference
Method
GD(STI)-102
(C)
(C) Crankshaft position sensor
NG judgment (Misfire occurrence judg-
ment required by the law) (Compare
number of misfire with judgment)
• FTP 1.5 times misfire NG judgment
• Catalyst damage misfire NG judgment
EN-01773