Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. 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

Perform the diagnosis only once when 5, 7 or 9.5 hours has passed after ignition switch is OFF. For more de-

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

(DTC) Detecting Criteria.>

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