Subaru LEGACY 2006 Manual page 512

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Diagnostic Trouble Code (DTC) Detecting Criteria
AI: DTC P0140 O2 SENSOR CIRCUIT NO ACTIVITY DETECTED (BANK1 SENSOR2)
1. OUTLINE OF DIAGNOSIS
Detect abnormalities in the rear oxygen sensor output characteristics.
By referring to the intake air amount, engine coolant temperature, main feedback control, deceleration fuel
cut and other operating conditions, if the rear oxygen sensor voltage should be moving under thoese condi-
tions but is showing a low voltage, this is judged as a Low side NG. If the voltage is showing a high voltage,
it is judged as a High side NG.
When either Low side or High side is NG, judged as rear oxygen sensor property NG.
2. ENABLE CONDITION
Secondary Parameters
Engine coolant temperature
Target output voltage of rear oxygen sen-
sor
Air intake amount
Battery voltage
Closed loop at the oxygen sensor
Misfire detection every 200 rotations
Front oxygen (A/F) sensor compensation
coefficient
Deceleration fuel cut of 5 seconds or
more.
3. GENERAL DRIVING CYCLE
Perform the diagnosis only once after engine warm-up.
4. DIAGNOSTIC METHOD
Abnormality Judgment
When one of the following conditions is established, judged as NG.
Judgment Value
Malfunction Criteria
Maximum output voltage low side diag-
nosis
Minimum output voltage high side diag-
nosis
Time Needed for Diagnosis: 200 seconds
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cy-
cles.
Normality Judgment
When the following conditions are established, judged as OK.
Judgment Value
Malfunction Criteria
Maximum output voltage low side diag-
nosis
Minimum output voltage high side diag-
nosis
5. DTC CLEAR CONDITION
• When the OK idling cycle is completed 40 times in a row
• When "Clear Memory" is performed
Enable Conditions
≥ 75°C (167°F)
≥ 0.6 V
10 g (0.35 oz)/seconds
or more
> 10.9 V
In operation
5 times or more
Not in limit value
Experienced
Threshold Value
< 0.55 V
> 0.25 V
Threshold Value
≥ 0.55 V
≤ 0.25 V
GD(H4SO)-75
GENERAL DESCRIPTION