Subaru Legacy IV (2008 year). Service manual — part 610

GD(H6DO)-60

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

AO:DTC P0137 O2 SENSOR CIRCUIT LOW VOLTAGE (BANK 1 SENSOR 2)

1. OUTLINE OF DIAGNOSIS

Detect continuity NG of the oxygen sensor. If the oxygen sensor voltage reading is not within the probable
range considering the operating conditions, judge as NG.

2. COMPONENT DESCRIPTION

(A)

Electromotive force

(C)

Rich

(E)

Theoretical air fuel ratio

(B)

Air fuel ratio

(D)

Lean

(F)

Comparative voltage

(1)

Atmosphere

(2)

Exhaust gas

(3)

Electromotive force

EN-01696

(3)

V

(1)

(2)

(2)

(E)

(F)

(C)

(B)

(D)

(A)

GD(H6DO)-61

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

3. ENABLE CONDITION

Used for abnormality judgment

Secondary Parameters

Enable Conditions

High

Secondary air system

Not in operation

Closed loop control at the oxygen sensor In operation

Misfire detection every 200 rotations

< 7 time(s)

Front oxygen (A/F) sensor compensation
coefficient

Not in limit value

Battery voltage

t 10.9 V

Engine coolant temperature

t 75 °C (167 °F)

Low (1)

Secondary air system

Not in operation

Closed loop control at the oxygen sensor In operation

Misfire detection every 200 rotations

< 7 time(s)

Front oxygen (A/F) sensor compensation
coefficient

Not in limit value

Battery voltage

t 10.9 V

Engine coolant temperature

t 75 °C (167 °F)

Amount of intake air

t 10 g/s (0.35 oz/s)

Low (2)

Secondary air system

Not in operation

Closed loop control at the oxygen sensor In operation

Misfire detection every 200 rotations

< 7 time(s)

Front oxygen (A/F) sensor compensation
coefficient

Not in limit value

Battery voltage

t 10.9 V

Engine coolant temperature

t 75 °C (167 °F)

Amount of intake air

< 10 g/s (0.35 oz/s)

Current continuation time of the rear oxy-
gen sensor heater

t 25000 ms

Low (3)

Secondary air system

Not in operation

Closed loop control at the oxygen sensor In operation

Misfire detection every 200 rotations

< 7 time(s)

Front oxygen (A/F) sensor compensation
coefficient

Not in limit value

Battery voltage

t 10.9 V

Engine coolant temperature

t 75 °C (167 °F)

Amount of intake air

< 10 g/s (0.35 oz/s)

Current continuation time of the rear oxy-
gen sensor heater

t 25000 ms

Fuel cut

Experienced

Used for normality judgment

Secondary Parameters

Enable Conditions

Secondary air system

Not in operation

Closed loop control at the oxygen sensor In operation

Misfire detection every 200 rotations

< 7 time(s)

Front oxygen (A/F) sensor compensation
coefficient

Not in limit value

Battery voltage

t 10.9 V

Engine coolant temperature

t 75 °C (167 °F)

GD(H6DO)-62

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

4. GENERAL DRIVING CYCLE

After starting the engine, continuously perform the diagnosis with the same engine condition.

5. DIAGNOSTIC METHOD

• Abnormality Judgement

If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.

Time Needed for Diagnosis:

High: 2500 ms
Low (1): 20000 ms
Low (2): 40000 ms
Low (3): Value from Map

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cy-
cles.

• Normality Judgement

Judge as OK and clear the NG if the continuous time while the following conditions are established is more
than the predetermined time.

Time Needed for Diagnosis:

High: Less than 1 second
Low (1): Less than 1 second
Low (2): Less than 1 second
Low (3): Less than 1 second

Judgement Value

Malfunction Criteria

Threshold Value

DTC

High

P0138

Sensor output voltage

> 1.200 V

P0158

Low

P0137

Sensor output voltage

< 0.030 V

P0157

Map

Fuel Cut Time (second)

0

2000

10000

Time needed for diagnosis (second)

40000

40000

60000

Judgement Value

Malfunction Criteria

Threshold Value

DTC

High

P0138

Sensor output voltage

d 1.200 V

P0158

Low

P0137

Sensor output voltage

t 0.030 V

P0157

GD(H6DO)-63

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

AP:DTC P0138 O2 SENSOR CIRCUIT HIGH VOLTAGE (BANK 1 SENSOR 2)

1. OUTLINE OF DIAGNOSIS

NOTE:
For the detection standard, refer to DTC P0137. <Ref. to GD(H6DO)-60, DTC P0137 O2 SENSOR CIRCUIT
LOW VOLTAGE (BANK 1 SENSOR 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>