Subaru 2009 IMPREZA Service Manual page 1703

Diagnostic Trouble Code (DTC) Detecting Criteria
0.04-inch Diagnosis
OK
Mode
Z
Mode
NG
Extend
Mode
Mode Z
(Purge control solenoid valve open-
ing failure diagnosis)
Mode A
(Estimated evaporation amount)
Mode B
(Sealed negative pressure, large
leakage judgement)
Mode C
(Pressure increase check,
advanced OK judgement)
Mode D
(Negative pressure variation measure-
ment, evaporation leakage diagnosis)
Mode Table for Evaporative Emission Control System Diagnosis
Behavior of tank internal pressure under
Mode
Roughly the same as barometric pres-
Mode Z
sure (Same as 0 kPa (0 mmHg, 0 inHg))
Pressure is in proportion to amount of
Mode A
evaporative emission.
Negative pressure is formed due to
Mode B
intake manifold negative pressure
Mode C Reaches target pressure
Mode D Pressure change is small.
OK OK
Mode
Mode
B
A
Large leakage judgement
Cancel
NG
Z
OK
Perform purge control solenoid valve opening failure diagnosis from
the size of tank pressure variation from diagnosis start.
Calculate the tank pressure change amount (P1).
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.
Wait until the tank pressure returns to the target (start level of P2 cal-
culation). If the tank pressure does not become the value, make
advanced OK judgement.
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.
normal conditions
GD(H4DOTC)-115
OK
Mode Mode
C D
NG
OK
Parge control
solenoid velve2
NG
blockade diagnosis
Early OK
Mode Description
Diagnostic item
Purge control solenoid valve is judged to
be open.
—
Large leak
—
EVAP system large leak determination
[1.0 mm (0.04 in)]
GENERAL DESCRIPTION
OK
END
Diagnosis Period
0 ms + 3000 ms —
0 ms + 3000 ms +
13000 ms
10000 ms
0 — 10000 ms +
25000 ms
0 — 18600 ms
0 ms + 10000 ms
DTC
P0457
None
P0457
None
P0442
EN-05590