Subaru 2009 IMPREZA Service Manual page 836

Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
Leak Diagnosis
DTC
P0456 Evaporative Emission Control System Leak Detected (very small leak)
• The diagnostic 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 not near 0 mmHg, 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.
Approx. 0 –2 kPa (0
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 the pressure change in the tank (P2), and measure the time
(evpdset) for the tank pressure to change to the Mode E shifting pressure. When the Mode E shifting pres-
sure is reached, Mode E is entered. If it does not change to the Mode E shifting pressure after the predeter-
mined amount of time has passed, make advanced OK judgement or cancel the diagnosis according to the
value of P2.
Normality Judgement
Judge as OK when the following conditions are established.
Judgement Value
Malfunction Criteria
Advanced OK judgement 1
Mode D time
Tank internal pressure
Advanced OK judgement 2
Mode D time
P2
Map 6
Fuel level (2, US gal, Imp gal)
Tank pressure (kPa, mmHg, inHgl)
Map 7
Fuel level (2, US gal, Imp gal)
Tank pressure (kPa, mmHg, inHgl)
–15 mmHg, 0 –0.6 inHg)
Threshold Value
0 ms + 10000 ms
Value of Map 6
0 ms + 200000 ms
Value of Map 7
10, 2.64,
0, 0, 0
2.2
–1.9, –1.9,
–14.62, –14.62,
–0.6 –0.6
10, 2.64,
0, 0, 0
2.2
0.9, 7, 0.3 0.9, 7, 0.3
GD(H4SO)-112
20, 5.28, 30, 7.93, 40, 10.57,
4.4 6.6
–1.9, –1.9,
–14.59, –14.56, –14.42,
–0.6 –0.6
20, 5.28, 30, 7.93, 40, 10.57,
4.4 6.6
0.9, 7.05, 0.9, 7.1, 1.1, 8.2,
0.3 0.3
50, 13.21, 60, 15.85,
8.8 11 13.2
–1.9, –1.9, –1.9,
–14.28, –14.28,
–0.6 –0.6 –0.6
50, 13.21, 60, 15.85,
8.8 11 13.2
1.3, 9.6, 1.3, 9.6,
0.3 0.4 0.4