Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Service manual — part 352
GD(H4DOTC)-160
Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
5. DIAGNOSTIC METHOD
• Abnormality Judgment
If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.
Time Needed for Diagnosis: 1000 ms
Malfunction Indicator Light Illumination: Illuminates as soon as a malfunction occurs.
• Normality Judgment
Judge as OK and clear the NG if the continuous time while the following conditions are established is more
than the predetermined time.
Time Needed for Diagnosis: Less than 1 second
Judgment Value
Malfunction Criteria
Threshold Value
Output voltage
≥ 4.095 V
Judgment Value
Malfunction Criteria
Threshold Value
Output voltage
< 4.095 V
GD(H4DOTC)-161
Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
CS:DTC P0455 EVAPORATIVE EMISSION SYSTEM LEAK DETECTED (LARGE
LEAK)
1. OUTLINE OF DIAGNOSIS
This diagnosis judges whether the ELCM operation is normal or not, and whether the evaporative emission
system has leak and clogging or not.
To purge the canister, after driving, perform the five hours soaking after ignition switch OFF in order to sta-
bilize the evaporative gas status. * After 5, 7 or 9.5 hours passed, ECM is activated by soaking timer, and the
leak check is started.
Judges whether the ELCM operation is normal or not, by measuring the reference pressure status via refer-
ence orifice (0.02 inch orifice). Judge as malfunction if the reference pressure is out of specified range. Then,
judge whether there is a leak or not, by comparing the pressure (leak pressure) when the reference pressure
and the evaporative emission system are in negative pressure condition. Judge as system leak in the evap-
orative emission system if the leak pressure is higher than reference pressure. Judge as clogging of pipe if
the leak pressure becomes lower than the reference pressure within the specified amount of time.
0.02 inch leak and 0.04 inch leak can be distinguished by measuring the leak pressure.
The diagnosis results are stored inside ECM until the engine is started again.
*: When the test conditions are not met in 5 hours, perform diagnosis at elapsed time of 7 hours. When the
test conditions are not met in 7 hours, perform diagnosis at elapsed time of 9.5 hours.
OUTLINE OF DIAGNOSIS
Diagnostic item
ELCM system (ELCM body)
Vacuum pump stuck
Switching valve stuck to open
Switching valve stuck to close
Reference orifice flow large
Reference orifice flow small
Leak check
Large leak
• 0.04 inch leak
• Fuel cap loose
• Fuel cap off
• System malfunction
Very small leak
• 0.02 inch leak
Clogging of pipe
—
EN-08949
ref
P
5 hours after ignition switch turned off.
ECM
Vacuum Pump
Switching Valve
Pressure Sensor
Leak detection pump stuck
Vent valve stuck open
Pipe clogging
OFF:Orifice side
OFF
OFF
ON:Evap. side
ON
ON
Very small leak
Large leak
Vent valve stuck close
Reference orifice high flow
Reference orifice low flow
ref
P
leak
P
GD(H4DOTC)-162
Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
2. COMPONENT DESCRIPTION
ELCM consists of the pressure sensor, the reference orifice (diameter of 0.02 inch), the vacuum pump which
introduces the negative pressure into evaporative emission system, and the switching valve which switches
the passage to introduce the negative pressure.
3. ENABLE CONDITIONS
(1)
ELCM
(5)
Vacuum pump
(9)
Fuel tank
(2)
Switching valve
(6)
Drain filter
(10) Canister
(3)
Reference orifice (0.02 inch ori-
fice)
(7)
Purge control solenoid valve
(4)
Pressure sensor
(8)
Intake manifold
Secondary Parameters
Enable Conditions
Activation of soaking timer
Completed
Battery voltage
≥ 10.9 V
Ignition switch
OFF
Engine coolant temperature
≥ 4.4 °C (39.9 °F)
and
< 45 °C (113 °F)
Atmospheric pressure
≥ 75 kPa (563 mmHg, 22.2 inHg)
and
< 110 kPa (825 mmHg, 32.5 inHg)
EVAP conc. learning during previous driving cycle
Done
Learning value of EVAP conc. during previous driving cycle
≤ 1
Accumulated purge amount during previous driving cycle
≥ Value of Map 1
Map 1
Engine coolant temperature
°C (°F)
0 (32)
30 (86)
35 (95)
40 (104)
45 (113)
Accumulated purge amount during previous
driving cycle
g (oz)
3000
(105.81)
3000
(105.81)
5000
(176.35)
7500
(264.53)
10000
(352.7)
EN-08957
M
(10)
(8)
(6)
(5)
(2)
(3)
(4)
(1)
(7)
(9)
GD(H4DOTC)-163
Diagnostic Trouble Code (DTC) Detecting Criteria
GENERAL DESCRIPTION
4. GENERAL DRIVING CYCLE
tail, refer to “OUTLINE OF DIAGNOSIS”. <Ref. to GD(H4DOTC)-161, OUTLINE OF DIAGNOSIS, DTC
P0455 EVAPORATIVE EMISSION SYSTEM LEAK DETECTED (LARGE LEAK), Diagnostic Trouble Code
5. DIAGNOSTIC METHOD
Mode
Explanation of Mode
Diagnosis Period
A
Vacuum pump operation confirmation and characteristics
stability
7 s or less & 300 s
B
Measurement of reference pressure for setting the target
negative pressure
40 s or less
C
Switching valve operation confirmation
12 s or less
D
Clogging of pipe diagnosis and leak pressure measure-
ment
900 s or less
E
Reference pressure measurement for judgment
40 s or less
EN-08950
Activated by soak timer
OFF:Orifice side
OFF
OFF
ON
ON
ON:Evap. side
Evap. System
target pressure calculation
A
B
C
D
E
Judge the leak is occurred or
not by comparing the pressures.
ECM
Vacuum Pump
Switching Valve
Pressure Sensor
Mode
EN-08956
ENABLE
CONDITION
satisfied
not satisfied
Mode
A
Mode
B
Mode
C
Mode
D
Mode
E
OK
OK
OK
OK
OK
NG
NG
NG
NG
NG
END
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