Subaru 2009 IMPREZA Service Manual page 784

Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
• 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
NOTE:
Variation time of rear oxygen sensor output voltage is short during fuel cut in deceleration. NG judgement
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 6000 ms or more, judge as NG if the following criteria are met 2000
ms after recovering from the deceleration fuel cut.
2) Judge as NG when the oxygen sensor voltage at recovery from a deceleration fuel cut is large.
If the fuel cut time in a deceleration fuel cut is long (6000 ms or more), and even after recovering from a de-
celeration fuel cut, the oxygen sensor voltage is high (0.55 V or more), judge as NG.
Judgement Value
Malfunction Criteria
Shortest time change from rich (0.5 V O
output) to lean (0.2 V) when voltage
reduces from 0.55 V to 0.15 V
or
Longest time over 0.55 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 rich (0.5 V O
output) to lean (0.2 V) when voltage
reduces from 0.55 V to 0.15 V
Time Needed for Diagnosis: 1 time(s)
6. ENABLE CONDITIONS
Lean rich response diagnosis
Secondary Parameters
Battery voltage
A/F main feedback control condition
Deceleration fuel cut time is 6000 ms or
more.
After fuel cut
Current calculation time of the rear oxy-
gen sensor heater
Current continuation time of the rear oxy-
gen sensor heater
Estimated catalyst temperature
Number of deceleration fuel cut
abnormal
Threshold Value
> 491 ms
2
2000 ms
Threshold value normal
Threshold Value
491 ms
2
Enable Condition
10.9 V
Completed
Experienced
2000 ms
60000 ms
30000 ms
450 °C (842 °F)
1 time(s)
GD(H4SO)-60