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Home >> Subaru >> 2020 >> Crosstrek Base, Automatic CVT Trans >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 24 (Engine Control System (Diagnostics) (HEV) (2 Of 4)) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P04EC: EVAP System Large Leak Detected - Fuel Tank Side >> General Description >> Diagnostic Method

Diagnostic Method

WARNING: This page is about a different variant/trim than selected.

Diagnosis flow varies depending on the tank pressure.

Diagnosis flow 1: When the tank pressure is within the specified value range.

G13237477Courtesy of SUBARU OF AMERICA, INC.
G13237478Courtesy of SUBARU OF AMERICA, INC.
Mode Explanation of Mode Diagnosis period DTC
A Vacuum pump operation confirmation and characteristics stability 7 s or less P2404
B Measurement of reference pressure for setting the target negative pressure 350 s or less P2404
C Switching valve operation confirmation 12 s or less P2404
Sealing valve open stuck P2450
D Leak pressure is being measured 900 s or less -
E Reference pressure measurement for canister side judgment 50 s or less P2404
Canister side 0.04 inch leak pressure measurement P04ED
Canister side 0.02 inch leak pressure measurement P04EF
F Tank side 0.04 inch leak advanced normal judgment 26 s or less P04EC
Tank side 0.02 inch leak advanced normal judgment P04EE
G Sealing valve close stuck 930 s or less P2451
H Tank side reference pressure measurement 50 s or less P2404
Tank side 0.04 inch leak pressure measurement P04EC
Tank side 0.02 inch leak pressure measurement P04EE

Diagnosis flow 2: When the tank pressure is out of the specified value range.

G13237479Courtesy of SUBARU OF AMERICA, INC.
G13237480Courtesy of SUBARU OF AMERICA, INC.
Mode Explanation of Mode Diagnosis period DTC
A Vacuum pump operation confirmation and characteristics stability 7 s or less P2404
B Measurement of reference pressure for setting the target negative pressure 350 s or less P2404
C Switching valve operation confirmation 12 s or less P2404
Sealing valve open stuck P2450
D Leak pressure is being measured 900 s or less -
E Reference pressure measurement for canister side judgment 50 s or less P2404
Canister side 0.04 inch leak pressure measurement P04ED
Canister side 0.02 inch leak pressure measurement P04EF
F Tank side 0.04 inch leak advanced normal judgment 26 s or less P04EC
Tank side 0.02 inch leak advanced normal judgment P04EE
I Sealing valve close stuck 15 s or less P2451

<Mode A (vacuum pump operation confirmation and characteristics stability)> 

Detect the vacuum pump operation trouble.

Judge as NG when the following conditions are established.

Judge as OK if the following conditions are not established, and warm up for five minutes to stabilize the vacuum pump characteristics.

Judgment value 

Malfunction Criteria Threshold Value DTC
Pressure sensor output value More than -224Pa (-1.68 mmHg, -0.1 inHg) P2404

<Mode B (measurement of reference pressure for setting the target negative pressure)> 

Judgment 1

Judge the reference pressure stability.

Judge as NG when the following conditions are established.

Judgment 2

Judge whether the reference pressure is within the normal range, and detect the vacuum pump and orifice malfunctions.

Judge as NG when the following conditions are established.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
Judgment 1
|Pressure sensor maximum output value - Pressure sensor minimum output value| Or,		 More than 314Pa (2.355 mmHg, 0.1 inHg) P2404
Judgment 2
Reference pressure for setting the target negative pressure		 Less than value of Map1
Or,
More than value of Map2		 P2404
MAP SPECIFICATION 1

Barometric pressure (kPa (mmHg, inHg)) 70 (525, 20.7) 80 (600, 23.6) 90 (675, 26.6) 100 (750, 29.5)
Reference pressure for setting the target negative pressure (kPa (mmHg, inHg)) -4 (-29.79, -1.2) -4.1 (-30.593, -1.2) -4.2 (-31.395, -1.2) -4.3 (-32.19, -1.3)
MAP SPECIFICATION 2

Barometric pressure (kPa (mmHg, inHg)) 70 (525, 20.7) 80 (600, 23.6) 90 (675, 26.6) 100 (750, 29.5)
Reference pressure for judgment (kPa (mmHg, inHg)) -0.9 (-7.065, -0.3) -1 (-7.86, -0.3) -1.2 (-8.663, -0.3) -1.3 (-9.465, -0.4)

<Mode C> 

Judgment 1 (Switching valve operation confirmation)

Measure the pressure increase when switching valve is changed from open to close, and detect the stuck to open/close malfunctions of the switching valve.

Judge as NG when the following conditions are established.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
Pressure sensor output value - Reference pressure for setting the target negative pressure Less than 224Pa (1.68 mmHg, 0.1 inHg) P2404

Judgment 2 (Sealing valve open stuck)

Judge as sealing valve open stuck if the amount of change of fuel tank pressure is equal to or larger than the specified value.

Detected as NG when the following conditions are established.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
Tank pressure reference value -2.6 kPa (-19.8 mmHg, -0.8 inHg) or more Or, 3.5 kPa (26.4 mmHg, 1 inHg) or less P2450
|Fuel tank pressure change amount| More than 0.9 kPa (7.065 mmHg, 0.3 in Hg)  

<Mode D (leak pressure measurement)> 

Judgment is not performed due to the time period of leak pressure measurement.

<Mode E (reference pressure measurement for canister side judgment)> 

Judgment 1

Judge the reference pressure stability.

Judge as NG when the following conditions are established.

Judgment 2

Judge whether the reference pressure is within the normal range, and detect the vacuum pump and orifice malfunctions. Judge the vacuum pump performance stability.

Judge as NG when the following conditions are established.

Judgment 3

Judge the presence of evaporative emission system leak.

Judge as NG when the following conditions are established.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
Judgment 1
|Pressure sensor maximum output value - Pressure sensor minimum output value|
Or,		 More than 314Pa (2.355 mmHg, 0.1 inHg) P2404
Judgment 2
Reference pressure for judgment
Or,		 Less than value of Map3 Or,
More than value of Map4		 P2404
Judgment 3
|Reference pressure for setting the target negative pressure - Reference pressure for judgment|		 More than 0.9 kPa (7.058 mmHg, 0.3 inHg) P2404
MAP SPECIFICATION 3

Barometric pressure (kPa (mmHg, inHg)) 70 (525, 20.7) 80 (600, 23.6) 90 (675, 26.6) 100 (750, 29.5)
Reference pressure for judgment (kPa (mmHg, inHg)) -4.5 (-34.02, -1.3) -4.6 (-34.815, -1.4) -4.7 (-35.618, -1.4) -4.9 (-36.42, -1.4)
MAP SPECIFICATION 4

Barometric pressure (kPa (mmHg, inHg)) 70 (525, 20.7) 80 (600, 23.6) 90 (675, 26.6) 100 (750, 29.5)
Reference pressure for judgment (kPa (mmHg, inHg)) -0.8 (-6.18, -0.2) -0.9 (-6.983, -0.3) -1 (-7.785, -0.3) -1.1 (-8.58, -0.3)

Judgment 4

Measure the pressure (leak pressure) when the evaporative emission system becomes the negative pressure by the vacuum pump.

Store the pressure as a leak pressure while the following conditions are met.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
<Large leak (0.04 inch)>Leak pressure Value of Map5 or more P04ED
<Very small leak (0.02 inch)>Leak pressure More than 0.018 inch reference pressure (Pa) and Less than value of Map5 P04EF
MAP SPECIFICATION 5

Reference pressure for judgment (Pa) -4856 -4000 -2750 -1500 -824
Threshold Value (Pa) -1785 -1463 -991 -520 -265

<Mode F (tank side leak advanced normal judgment)> 

Judge as normal if the fuel tank pressure is within the specified value range, and go to the diagnosis flow 2.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
Fuel tank pressure 3.5 kPa (26.4 mmHg, 1 inHg) or more Or, -2.6 kPa (-19.8 mmHg, -0.8 inHg) or less P04EC or P04EE

<Mode G (sealing valve close stuck)> 

Judge as sealing valve close stuck if the amount of change of fuel tank pressure is equal to or smaller than the amount of change of Evaporative Leak Control Module pressure.

Detected as NG when the following conditions are established.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
Fuel tank pressure change amount - Fuel tank pressure More than 0.8 kPa (6.18 mmHg, 0.2 inHg) P2451

<Mode H (tank side reference pressure measurement)> 

Judgment 1

Judge the reference pressure stability.

Judge as NG when the following conditions are established.

Judgment 2

Judge whether the reference pressure is within the normal range, and detect the vacuum pump and orifice malfunctions. Judge the vacuum pump performance stability.

Judge as NG when the following conditions are established.

Judgment 3

Judge the presence of evaporative emission system leak.

Judge as NG when the following conditions are established.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
Judgment 1
Pressure sensor maximum output value - Pressure sensor minimum output value| Or,		 More than 314Pa P2404
Judgment 2
Reference pressure for judgment		 Less than value of Map6 Or, More than value of Map7 P2404
Judgment 3
|Reference pressure for setting the target negative pressure - Reference pressure for judgment|		 More than 941Pa P2404
MAP SPECIFICATION 6

Barometric pressure (kPa (mmHg, inHg)) 70 (525, 20.7) 80 (600, 23.6) 90 (675, 26.6) 100 (750, 29.5)
Reference pressure for judgment (kPa (mmHg, inHg)) -4.5 (-34.02, -1.3) -4.6 (-34.815, -1.4) -4.7 (-35.618, -1.4) -4.9 (-36.42, -1.4)
MAP SPECIFICATION 7

Barometric pressure (kPa (mmHg, inHg)) 70 (525, 20.7) 80 (600, 23.6) 90 (675, 26.6) 100 (750, 29.5)
Reference pressure for judgment (kPa (mmHg, inHg)) -0.8 (-6.18, -0.2) -0.9 (-6.983, -0.3) -1 (-7.785, -0.3) -1.1 (-8.58, -0.3)

Judgment 4

Measure the pressure (leak pressure) when the evaporative emission system becomes the negative pressure by the vacuum pump.

Store the pressure as a leak pressure while the following conditions are met.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
<Large leak (0.04 inch)>
Leak pressure		 Value of Map5 or more P04EC
<Very small leak (0.02 inch)>Leak pressure 0.018 inch reference pressure (Pa) and Less than value of Map5 P04EE
MAP SPECIFICATION 5

Reference pressure for judgment (Pa) -4856 -4000 -2750 -1500 -824
Threshold Value (Pa) -1785 -1463 -991 -520 -265

<Mode I (sealing valve close stuck)> 

Judge as sealing valve close stuck if the amount of change of fuel tank pressure is within the specified value range.

Detected as NG when the following conditions are established.

JUDGMENT VALUE SPECIFICATION

Malfunction Criteria Threshold Value DTC
|Fuel tank pressure change amount| -0.5 kPa (-3.75 mmHg, -0.1 inHg) or more and 0.5 kPa (3.75 mmHg, 0.1 in Hg) or less P2451

Time needed for diagnosis: 

Malfunction indicator light illumination:  Illuminates when malfunction occurs in 2 continuous driving cycles.

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