Subaru Legacy IV (2008 year). Manual - part 393

GD(H4DOTC)-22

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

I:

DTC P0038 HO2S HEATER CONTROL CIRCUIT HIGH (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 High.

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)

High 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-01793

(C)

(A)

(B)

ON

OFF

0V

(D)

GD(H4DOTC)-23

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:8 ms × 320 time(s)
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: Less than 1 second

Judgement Value

Malfunction Criteria

Threshold Value

Output voltage level

High

Rear oxygen sensor heater control duty

t 25 %

Judgement Value

Malfunction Criteria

Threshold Value

Output voltage level

Low

GD(H4DOTC)-24

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

J: DTC P0068 MAP/MAF - THROTTLE POSITION CORRELATION

1. OUTLINE OF DIAGNOSIS

Detect problems in the intake manifold pressure sensor output properties.
Judge as NG when the intake air pressure AD value is Low whereas it seemed to be High from the viewpoint
of engine condition, or when it is High whereas it seemed to be Low from the engine condition.

2. COMPONENT DESCRIPTION

3. ENABLE CONDITION

4. GENERAL DRIVING CYCLE

Perform the diagnosis continuously after idling.

(A)

Output voltage

(B)

Absolute pressure

(1)

Connector

(2)

Terminals

(3)

O-ring

Secondary Parameters

Enable Conditions

Engine coolant temperature

t 70 °C (158 °F)

EN-01765

(B)

(A)

(2)

(3)

(1)

GD(H4DOTC)-25

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

5. DIAGNOSTIC METHOD

• Abnormality Judgement

Judge as NG when Low side or High side becomes NG.
If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.

Time Needed for Diagnosis:
Low side: 3000 ms
High side: 3000 ms
Malfunction Indicator Light Illumination:  Illuminates when malfunction occurs in 2 continuous driving cy-
cles.

• Normality Judgement

Judge as OK and clear the NG when both Low side and High side become OK.
If the duration of time while the following conditions are met is longer than the time indicated, judge as OK.

Time Needed for Diagnosis:
Low side: Less than 1 second
High side: Less than 1 second

Judgement Value

Malfunction Criteria

Threshold Value

Low

Engine speed

< 2500 rpm

Throttle position

t 10 °

Output voltage

< 1 V

Engine load

> 1.356 g/rev (0.05 oz/rev)

High

Engine speed

600 rpm — 900 rpm

Throttle position

< 2.75 °

Output voltage

t 2.36 V

Engine load

< 0.4 g/rev (0.01 oz/rev)

Judgement Value

Malfunction Criteria

Threshold Value

Low

Engine speed

< 2500 rpm

Throttle position

t 10 °

Output voltage

t 1 V

Engine load

> 1.356 g/rev (0.05 oz/rev)

High

Engine speed

600 rpm — 900 rpm

Throttle position

< 2.75 °

Output voltage

< 2.36 V

Engine load

< 0.4 g/rev (0.01 oz/rev)