Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual - part 319

GD(H4DOTC)-28

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

T: 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 CONDITIONS

4. GENERAL DRIVING CYCLE

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

(A)

Battery voltage

(B)

Output voltage of the rear oxygen 
sensor heater

(C)

256 ms (cycles)

(D)

Low error

 

 

 

 

Secondary Parameters

Enable Conditions

Battery voltage

≥ 10.9 V

Elapsed time after engine starting

≥ 1 second

Engine speed

< 8000 rpm

EN-01792

(C)

(A)

(B)

ON

OFF

0V

(D)

GD(H4DOTC)-29

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

5. DIAGNOSTIC METHOD

• Abnormality Judgment
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 × 1250 time(s)

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

cles.
• Normality Judgment
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

Judgment Value

Malfunction Criteria

Threshold Value

Output voltage level

Low

Rear oxygen sensor heater control duty

< 75 %

Judgment Value

Malfunction Criteria

Threshold Value

Output voltage level

High

GD(H4DOTC)-30

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

U: 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 CONDITIONS

4. GENERAL DRIVING CYCLE

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

(A)

Battery voltage

(B)

Output voltage of the rear oxygen 
sensor heater

(C)

256 ms (cycles)

(D)

High error

 

 

 

 

Secondary Parameters

Enable Conditions

Battery voltage

≥ 10.9 V

Elapsed time after engine starting

≥ 1 second

Engine speed

< 8000 rpm

EN-01793

(C)

(A)

(B)

ON

OFF

0V

(D)

GD(H4DOTC)-31

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

5. DIAGNOSTIC METHOD

• Abnormality Judgment
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 Judgment
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

Judgment Value

Malfunction Criteria

Threshold Value

Output voltage level

High

Rear oxygen sensor heater control duty

≥ 25 %

Judgment Value

Malfunction Criteria

Threshold Value

Output voltage level

Low