Subaru Legacy IV (2008 year). Service 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
Z
Mode
A
Mode
B
Mode
C
Mode
D
OK
OK
OK
OK
OK
NG
Early OK
Large leakage judgement
Cancel
Mode
Z
Extend
NG
NG
OK
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)
0
10, 2.64,
2.2
20, 5.28,
4.4
30, 7.93,
6.6
40, 10.57,
8.8
50, 13.21,
11
60, 15.85,
13.2
Time Needed for Diagnosis (ms)
12000
12000
11000
10000
7500
5000
5000
Map2
Fuel level (
2, US gal, Imp gal)
0
10, 2.64,
2.2
20, 5.28,
4.4
30, 7.93,
6.6
40, 10.57,
8.8
50, 13.21,
11
60, 15.85,
13.2
Time Needed for Diagnosis (ms)
18500
18500
18500
18500
18500
18500
18500
Map 3
Fuel level (
2, US gal, Imp gal)
0
10, 2.64,
2.2
20, 5.28,
4.4
30, 7.93,
6.6
40, 10.57,
8.8
50, 13.21,
11
60, 15.85,
13.2
Time Needed for Diagnosis (ms)
60000
60000
60000
60000
60000
60000
60000
EN-02871
Mode A
Mode B
Mode C
Mode D
Mode E
Cancel
Early OK 2
Early OK 1
OK
OK
OK
OK
Cancel
Cancel
Cancel
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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