Subaru 2009 IMPREZA Service Manual page 1651

Diagnostic Trouble Code (DTC) Detecting Criteria
• Abnormality Judgement
1) Judge as NG when the judgement value is larger than the threshold value after deceleration fuel cut.
Response time (diagnosis value) > threshold value
2) If the oxygen sensor voltage is small after recovering from a deceleration fuel cut, and remains small,
judge as NG.
Judgement Value
Malfunction Criteria
Shortest time change from lean (0.3 V
O output) to rich (0.5 V) when voltage
2
changes from 0.25 V to 0.55 V
or
Longest time under 0.25 V
Time Needed for Diagnosis: 1 time(s)
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cy-
cles.
• Normality Judgement
1) Regardless of a deceleration fuel cut, if the response time (diagnosis value) when the oxygen sensor volt-
age has changed from rich to lean is shorter than the threshold value (judgement value), judge as a normal
condition.
Response time (diagnosis value)
2) Do not judge as a normal condition.
Judge as OK and clear the NG if the following conditions are established.
Judgement Value
Malfunction Criteria
Shortest time change from lean (0.3 V
O output) to rich (0.5 V) when voltage
2
changes from 0.25 V to 0.55 V
Time Needed for Diagnosis: 1 time(s)
abnormal
Threshold Value
> 4000 ms
120000 ms
threshold value normal
Threshold Value
4000 ms
GD(H4DOTC)-63
GENERAL DESCRIPTION