Subaru Legacy IV (2008 year). Manual - part 627

GD(H6DO)-128

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

CG:DTC P0451 EVAPORATIVE EMISSION CONTROL SYSTEM PRESSURE 

SENSOR

1. OUTLINE OF DIAGNOSIS

Detect the tank pressure sensor output property abnormality.
Judge as NG when there is no pressure variation, which should exist in the tank, considering the engine sta-
tus.

2. COMPONENT DESCRIPTION

3. ENABLE CONDITION

4. GENERAL DRIVING CYCLE

• Perform the diagnosis continuously after 60 s have passed since the engine started.
• Pay attention to the fuel level and temperature.

(A)

Output voltage

(B)

Input voltage

(C)

To fuel tank

(1)

Connector

(2)

Terminals

Secondary Parameters

Enable Conditions

Elapsed time after starting the engine

t 60 s

Fuel level

t 9.6 

2 (2.54 US gal, 

2.11 Imp gal)

Fuel temperature

< 35 °C (95 °F)

Battery voltage

t 10.9 V

Barometric pressure

t 75 kPa (563 mmHg, 
22.2 inHg)

EN-04462

(A)

(B)

(2)

(1)

(C)

GD(H6DO)-129

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.

If the difference between the Max. fuel level every 60 s and Min. fuel level every 60 s is less than 2 

2 (0.53

US gal, 0.44 Imp gal), extend 60 s and make judgement with the Max. and Min. values for the fuel level in 60
s × 2. If a difference does not appear, extend the time (60 s × 3, 60 s × 4, 60 s × 5) and continue the judge-
ment. If the difference between the Max. fuel level every 60 s and Min. fuel level every 60 s is 2 

2 (0.53 US

gal, 0.44 Imp gal) or more, the diagnosis counter counts up.
Time Needed for Diagnosis: 60 s × 16 time(s) or more
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

Number of times that the difference 
between the Max. fuel level every 60 s 
and Min. fuel level every 60 s is 2 

2

(0.53 US gal, 0.44 Imp gal) or more (with 
enable condition established)

t 16 time(s)

Maximum – Minimum tank pressure 
(with enable condition completed)

< 0 kPa (0.375 mmHg, 
0 inHg)

Maximum – Minimum fuel temperature 
(with enable condition completed)

t 7 °C (44.6 °F)

Judgement Value

Malfunction Criteria

Threshold Value

Maximum — Minimum tank pressure

t 0 kPa (0.375 mmHg, 
0 inHg)

GD(H6DO)-130

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

CH:DTC P0452 EVAPORATIVE EMISSION CONTROL SYSTEM PRESSURE 

SENSOR LOW INPUT

1. OUTLINE OF DIAGNOSIS

Detect the open or short circuit of the fuel tank pressure sensor.
Judge as NG if out of specification.

2. COMPONENT DESCRIPTION

3. ENABLE CONDITION

4. GENERAL DRIVING CYCLE

Always perform the diagnosis continuously.

(A)

Output voltage

(B)

Input voltage

(C)

To fuel tank

(1)

Connector

(2)

Terminals

Secondary Parameters

Enable Conditions

None

 

EN-04462

(A)

(B)

(2)

(1)

(C)

GD(H6DO)-131

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: 15000 ms
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

Fuel tank pressure

< –7.4 kPa (–55.85 mmHg, 
–2.2 inHg)

Battery voltage

t 10.9 V

Judgement Value

Malfunction criteria

Threshold value

Fuel tank pressure

t –7.4 kPa (–55.85 mmHg, 
–2.2 inHg)

Battery voltage

t 10.9 V