Subaru Legacy IV (2008 year). Manual - part 391

GD(H4DOTC)-14

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

E: DTC P0030 HO2S HEATER CONTROL CIRCUIT (BANK 1 SENSOR 1)

1. OUTLINE OF DIAGNOSIS

Detect functional errors of the front oxygen (A/F) sensor heater.
Judge as NG when it is determined that the front oxygen (A/F) sensor impedance is large when looking at en-
gine status such as deceleration fuel cut.

2. COMPONENT DESCRIPTION

3. ENABLE CONDITION

4. GENERAL DRIVING CYCLE

Perform the diagnosis continuously after 42000 ms or more have passed since the engine started.

(1)

Gasket

(3)

Sensor housing

(4)

Protection tube

(2)

Ceramic 

heater

  

  

Secondary Parameters

Enable Conditions

Condition established time

t 42000 ms

Battery voltage

t 10.9 V

Heater current

Permitted

Control duty 

t 35 %

Experienced

After fuel cut

t 20000 ms

EN-02181

( 1 )

( 2 )

( 3 )

( 4 )

GD(H4DOTC)-15

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: 10000 ms
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: 10000 ms

Judgement Value

Malfunction Criteria

Threshold Value

Front oxygen (A/F) sensor impedance

> 50 

:

Judgement Value

Malfunction Criteria

Threshold Value

Front oxygen (A/F) sensor impedance

d 50 :

GD(H4DOTC)-16

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

F: DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW (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 Low.

2. COMPONENT DESCRIPTION

3. ENABLE CONDITION

4. GENERAL DRIVING CYCLE

Always perform the diagnosis continuously.

(A)

Battery voltage

(C)

128 milliseconds

(D)

Low error

(B)

Front oxygen (A/F) sensor heater 
output voltage

 

 

 

 

Secondary Parameters

Enable Conditions

Battery voltage

t 10.9 V

EN-01792

(C)

(A)

(B)

ON

OFF

0V

(D)

GD(H4DOTC)-17

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