Subaru IMPREZA GD 2007 Series Manual page 2208

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Diagnostic Trouble Code (DTC) Detecting Criteria
Leak Diagnosis
DTC
P0456 Evaporative Emission Control System Leak Detected (very small leak)
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: (0 point compensation)
When the pressure in the tank is high, wait until it returns to 0 point (Near 0 mmHg,). Shift to mode B when
returned to the 0 point. Cancel the diagnosis when 0 point does not return in the specified time.
Mode B: (Negative pressure introduced)
Introduce negative pressure in the intake manifold to the tank.
Approximately 0 → –2.0 kPa (0 → –15 mmHg, 0 → –0.59 inHg)
When the pressure above (desired negative pressure) is reached, enters Mode C.
When the tank internal pressure does not reach the target negative pressure, the diagnosis is cancelled.
Mode C: (Negative pressure maintained)
Stop the introduction of negative pressure. (Wait until the tank pressure returns to the start level of P2 cal-
culation.)
Change to Mode D either when the tank pressure returns to the start level of P2 calculation, or when the pre-
determined amount of time has passed.
Mode D: (Calculate the amount of negative pressure change)
Monitor the tank pressure in mode D, calculate (P2) the pressure change in the tank, and measure the time
(evpdset) for the tank pressure to return when calculation of P2 is completed. Change to Mode E when the
tank pressure returns to the end level of P2 calculation. If it does not return to the P2 calculation end tank in-
ternal pressure after the predetermined amount of time has passed, make advanced OK judgment or cancel
the diagnosis.
Normality Judgment
Judge as OK if the criteria below are met.
Judgment Value
Malfunction Criteria
Advanced OK judgment 1
Mode D time
Tank internal pressure
Advanced OK judgment 2
Mode D time
P2
Mode E: (Evaporation occurrence amount calculation)
Calculate the change of tank pressure with the time evpdset to judge as NG/OK according to the value of P1.
(ambiguous determination acceptable).
Abnormality Judgment
Judge as NG if the criteria below are met.
Judgment Value
Malfunction Criteria
P1
Threshold Value
≥ 30 seconds
≤ –1.8 kPa (–13.4 mmHg, –0.53
inHg)
≥ 200 seconds
≤ 0.9 — 1.3 kPa (7 — 9.6 mmHg,
0.28 — 0.38 inHg)
Threshold Value
< Value from Map 3
* Threshold value: Map
(Remaining fuel level vs. evpdset)
GD(STI)-141
GENERAL DESCRIPTION