Subaru IMPREZA GD 2007 Series Manual page 1860

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Diagnostic Trouble Code (DTC) Detecting Criteria
4. GENERAL DRIVING CYCLE
In order to figure out the diagnostic value, perform the diagnosis only once when deceleration fuel cut occurs
after rapid acceleration. (Pay attention to the oxygen sensor voltage for the timing of the deceleration.)
5. DIAGNOSTIC METHOD
When the rear oxygen sensor output voltage changes from 0.55 V (rich) to 0.15 V (lean), calculate the min-
imum response time for output change between 0.5 V and 0.2 V for the judgment criteria.
Diagnosis execution condition
Rear oxygen sensor (V)
0V
Fuel cut on deceleration
Abnormality Judgment
1) Judge as NG when the judgment value is larger than the threshold value after deceleration fuel cut.
Response time (diagnosis value) > threshold value → abnormal
NOTE:
Variation time of rear oxygen sensor output voltage is short during fuel cut in deceleration. NG judgment
should be performed after deceleration fuel cut. Even without deceleration fuel cut, judge as OK if the value
is below the threshold.
When the deceleration fuel cut time is 6 seconds or more, judge as NG if the following criteria are met 2 sec-
onds after recovering from the deceleration fuel cut.
0.55V
0.5V
0.2V
0.15V
More than 6 seconds
GD(H4DOTC)-69
GENERAL DESCRIPTION
Measure the response time.
Execute the malfunction judgment
2 seconds after the recovery of fuel.
EN-05554