Subaru Legacy IV (2008 year). Service manual — part 178

GD(H4SO)-14

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

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:4 ms × 250 time(s)
Malfunction Indicator Light Illumination: Illuminates as soon as a malfunction occurs.

• 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: Less than 1 second

Judgement Value

Malfunction Criteria

Threshold Value

Output voltage level

Low

Front oxygen (A/F) sensor heater control
duty

< 87.5 %

Judgement Value

Malfunction Criteria

Threshold Value

Output voltage level

High

GD(H4SO)-15

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

E: DTC P0032 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 1)

1. OUTLINE OF DIAGNOSIS

Detect front oxygen (A/F) sensor heater open or short circuit.
The front oxygen (A/F) sensor heater performs duty control, and the output terminal voltage at ON is 0 V, and
the output terminal voltage at OFF is the battery voltage.
Judge as NG when the terminal voltage remains High.

2. COMPONENT DESCRIPTION

3. ENABLE CONDITION

4. GENERAL DRIVING CYCLE

Always perform the diagnosis continuously.

(A)

Battery voltage

(C)

128 milliseconds

(D)

High error

(B)

Front oxygen (A/F) sensor heater
output voltage

Secondary Parameters

Enable Conditions

Battery voltage

t 10.9 V

EN-01793

(C)

(A)

(B)

ON

OFF

0V

(D)

GD(H4SO)-16

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

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:4 ms × 500 time(s)
Malfunction Indicator Light Illumination: Illuminates as soon as a malfunction occurs.

• 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: Less than 1 second

Judgement Value

Malfunction Criteria

Threshold Value

Output voltage level

High

Front oxygen (A/F) sensor heater control
duty

t 12.5 %

Judgement Value

Malfunction Criteria

Threshold Value

Output voltage level

Low

GD(H4SO)-17

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

F: DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)

1. OUTLINE OF DIAGNOSIS

Detect the rear oxygen sensor heater open or short circuit.
The rear oxygen sensor heater performs duty control, and the output terminal voltage at ON is 0 V, and the
output terminal voltage at OFF is the battery voltage.
Judge as NG when the terminal voltage remains Low.

2. COMPONENT DESCRIPTION

3. ENABLE CONDITION

4. GENERAL DRIVING CYCLE

After starting the engine, perform the diagnosis continuously when engine is low speed.

(A)

Battery voltage

(C)

256 milliseconds (cycles)

(D)

Low error

(B)

Output voltage of the rear oxygen
sensor heater

Secondary Parameters

Enable Conditions

Battery voltage

t 10.9 V

Elapsed time after engine starting

t 1 second

Engine speed

< 8000 rpm

EN-01792

(C)

(A)

(B)

ON

OFF

0V

(D)