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Subaru Legacy IV (2008 year). Manual - part 622

GD(H6DO)-108

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

CD:DTC P0442 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED

(SMALL LEAK)

1. OUTLINE OF DIAGNOSIS

Check if there is a leakage in fuel system or not, and perform the function diagnosis of valve.

In this system diagnosis, check for leakage and valve function is conducted by changing the fuel tank pres-
sure and monitoring the pressure change using the fuel tank pressure sensor. When in 0.04 inch diagnosis,
perform in the order of mode Z

o mode A o mode B o mode C and mode D; When in 0.02 inch diagnosis,

perform in the order of mode A

o mode B o mode C o mode D and mode E.

(1)

Fuel gauge

(7)

Pressure control valve

(12)

Fuel level sensor

(2)

Intake manifold

(8)

Drain valve

(13)

Fuel tank

(3)

Throttle body

(9)

Drain filter

(14)

Fuel cut valve

(4)

Purge control solenoid valve

(10)

Shut-off valve

(15)

Fuel tank pressure sensor

(5)

Engine control module (ECM)

(11)

Fuel temperature sensor

(16)

Vent valve

(6)

Canister

(1)

(2)

(3)

(4)

(5)

(7)

(8)

(9)

(6)

(11)

(10)

(12)

(13)

(16)

(14)

(15)

EN-04151

GD(H6DO)-109

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

0.04-inch Diagnosis

Mode Table for Evaporative Emission Control System Diagnosis

Mode

Mode Description

Diagnosis Period

Mode Z

(Purge control solenoid valve

opening failure diagnosis)

Perform purge control solenoid valve opening failure diagnosis from
the size of tank pressure variation from diagnosis start.

0 ms + 3000 ms — 0 ms

+ 3000 ms + 13000 ms

Mode A

(Estimated evaporation amount)

Calculate the tank pressure change amount (P1).

10000 ms

Mode B

(Sealed negative pressure,

large leakage judgement)

Decrease the pressure in the tank to the target value by introducing
the intake manifold pressure to the fuel tank.
If the tank pressure cannot be reduced, it is diagnosed as large leak.

0 — 10000 ms

+ 25000 ms

Mode C

(Pressure increase check,

advanced OK judgement)

Wait until the tank pressure returns to the target (start level of P2
calculation). If the tank pressure does not become the value, make
advanced OK judgement.

0 — 17000 ms

Mode D

(Negative pressure variation

measurement, evaporation

leakage diagnosis)

Calculate the tank pressure variation (P2), and obtain the diagnostic
value using P1 found in Mode A.
Perform the evaporation diagnosis using the diagnostic value.

0 ms + 10000 ms

Mode

Behavior of tank internal pressure under

normal conditions

Diagnostic item

DTC

Mode Z

Roughly the same as barometric pres-
sure (Same as 0 kPa (0 mmHg, 0 inHg))

Purge control solenoid valve is judged to
be open.

P0457

Mode A

Pressure is in proportion to amount of
evaporative emission.

—

None

Mode B

Negative pressure is formed due to
intake manifold negative pressure

Large leak

P0457

Mode C

Reaches target pressure

—

None

Mode D

Pressure change is small.

EVAP system large leak determination.
[1.0 mm (0.04 in)]

P0442

Mode

Early OK

Large leakage judgement

Cancel

Mode

Extend

END

EN-02872

GD(H6DO)-110

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

0.02-inch Diagnosis

Mode

Mode Description

Diagnosis Period

Mode A

(0 point compensation)

When the pressure in the tank is not near 0 mmHg, wait until it
returns to 0 point (near 0 mmHg).

0 — Value of Map 1

Mode B

(Negative pressure introduced)

Decrease the pressure in the tank to the target value by introducing
the intake manifold pressure to the fuel tank.

0 — Value of Map 2

Mode C

(Negative pressure maintained)

Wait until the tank pressure returns to the target (start level of P2
calculation).

0 — 20000 ms + 0

+ Value from Map 2

Mode D

(Negative pressure change

calculated)

Calculate the time it takes for the tank pressure to change to the
Mode E shifting pressure. If the tank pressure does not change to
the Mode E shifting pressure, make advanced OK judgement.

0 — 0 ms + 200000 ms

Mode E

(Evaporation generated amount

calculation)

Calculate the amount of evaporation (P1).

0 — 0 ms + 200000 ms

+ Value from Map 3

Map1

Fuel level (

2, US gal, Imp gal)

10, 2.64,

2.2

20, 5.28,

4.4

30, 7.93,

6.6

40, 10.57,

8.8

50, 13.21,

60, 15.85,

13.2

Time Needed for Diagnosis (ms)

12000

11000

10000

7500

5000

Map2

Fuel level (

2, US gal, Imp gal)

10, 2.64,

2.2

20, 5.28,

4.4

30, 7.93,

6.6

40, 10.57,

8.8

50, 13.21,

60, 15.85,

13.2

Time Needed for Diagnosis (ms)

18500

Map 3

Fuel level (

2, US gal, Imp gal)

10, 2.64,

2.2

20, 5.28,

4.4

30, 7.93,

6.6

40, 10.57,

8.8

50, 13.21,

60, 15.85,

13.2

Time Needed for Diagnosis (ms)

60000

EN-02871

Mode A

Mode B

Mode C

Mode D

Mode E

Cancel

Early OK 2

Early OK 1

Cancel

END

GD(H6DO)-111

Diagnostic Trouble Code (DTC) Detecting Criteria

GENERAL DESCRIPTION

2. COMPONENT DESCRIPTION

Pressure control solenoid valve

PCV controls the fuel tank pressure to be equal to the atmospheric air pressure. Normally, the solenoid is set
to OFF. The valve opens and closes mechanically in accordance with the pressure difference between tank
and atmospheric air, or tank and canister.
The valve is forcibly opened by setting the solenoid to ON at the time of diagnosis.

(a)

Barometric pressure

(b)

Fuel tank

(c)

Canister

(1)

Solenoid

(3)

Valve

(4)

Spring

(2)

Diaphragm

EN-01715

(a)

(b)

(c)

(4)

(1)

(2)

(3)

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