Subaru LEGACY 2006 Manual page 511

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Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
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
2. If the oxygen sensor voltage is small after recovering from a deceleration fuel cut, and remains small,
judge as NG.
Judgment Value
Malfunction Criteria
Shortest time change from lean (300 mV
O2 output) to rich (500 mV) when volt-
age drops from 500 mV to 250 mV.
Time at less than 250 mv
Time Needed for Diagnosis: 1 time
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cy-
cles.
Normality Judgment
1. Regardless of a deceleration fuel cut, if the response time (diagnosis value) when the oxygen sensor
voltage has changed from rich to lean is shorter than the threshold value (judgment value), judge as a normal
condition.
Response time (diagnosis value) ≤ threshold value → normal
2. Do not judge as a normal condition.
Judge as OK when the criteria below are met.
Judgment Value
Malfunction Criteria
Shortest time change from lean (300 mV
O2 output) to rich (500 mV) when volt-
age drops from 550 mV to 250 mV.
13.DTC CLEAR CONDITION
• When the OK idling cycle is completed 40 times in a row
• When "Clear Memory" is performed
14.MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
• When the OK driving cycle is completed 3 times in a row
• When "Clear Memory" is performed
15.FAIL SAFE
Sub feedback control: Not allowed.
16.ECM OPERATION AT DTC SETTING
• Memorize the freeze frame data. (For test mode $02)
• Memorize the diagnostic value and trouble standard value. (For test mode $06)
Threshold Value
> 2 sec.
> 120 sec.
Threshold Value
≤ 2 sec.
GD(H4SO)-74