Subaru IMPREZA GD 2007 Series Manual page 1932

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Diagnostic Trouble Code (DTC) Detecting Criteria
Leak Diagnosis
DTC
P0441 CPC2 solenoid property (close)
P0442 Evaporative Emission Control System Leak Detected (Small Leak)
P0457 Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)
Diagnostic method
• The diagnostic method consists of creating a sealed vacuum in the fuel tank and then determining the
presence of leakage from the speed at which the tank internal pressure returns to barometric pressure.
• The diagnosis is divided into the following five phases.
Mode A: (Estimated evaporation gas amount)
Calculate the tank pressure change amount (P1) when using mode A. After calculating P1, switch to mode B.
Mode B: (Negative pressure sealed)
Introduce negative pressure in the intake manifold to the tank.
Approximately 0 → –1.4 kPa (0 → –10.5 mmHg, 0 → –0.41 inHg)
When the pressure above (desired negative pressure) is reached, enters Mode C.
In this case, if the tank pressure does not reach the target negative pressure, judge that there is a large leak-
age (10 seconds or 25 seconds) in the system and terminate the evaporative emission control system diag-
nosis.
Abnormality Judgment
Judge as NG (large leak) when the criteria below are met.
Judgment Value
Malfunction Criteria
Time to reach target negative pressure
Or mode B time
(Min. pressure value in tank when in
mode B) – (Tank pressure when mode B
started)
Mode C: (Check pressure rise)
Stop the introduction of negative pressure. (Wait until the tank pressure returns to the start level of P2 cal-
culation.)
Change to Mode D when the tank pressure returns to the start level of P2 calculation.
Judge immediate OK and perform purge control solenoid valve 2 stuck close diagnosis when it does not re-
turn after the specified time passed.
Tank pressure when starting cal-
culation of P2
–1.3 kPa (–9.75 mmHg, –0.38
inHg)
Purge control solenoid valve 2 stuck close diagnosis
Perform purge control solenoid valve 2 stuck close diagnosis using the variation gap between the tank pres-
sure at the end of mode C and after mode C.
Judgment Value
Malfunction Criteria
Tank pressure variation after the end of
mode C
Mode D: (Measure amount of negative pressure change)
Monitor the tank pressure change amount when using mode D. In this case, the tank pressure increases,
(nears barometric pressure) because evaporation occurs. However, if any leakage exists, the pressure in-
creases additionally in proportion to this leakage. The pressure variation of this tank is P2.
After calculating P2, perform a small leak diagnosis according to the items below.
Threshold Value
≥ 25 seconds
≥ 10 seconds
< –0.5 kPa (–4 mmHg,
–0.016 inHg)
Time for advanced OK
judgment
15 seconds
Threshold Value
3.5 seconds
< 0.1 kPa (0.75 mmHg,
0.03 inHg)
GD(H4DOTC)-141
GENERAL DESCRIPTION
DTC
P0457
DTC
P0441