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Home >> Subaru >> 2006 >> Legacy GT spec.B >> Repair and Diagnosis (Single Page) >> Engine Performance >> Testing & Diagnosis >> Diagnostic Trouble Code (DTC) Detecting Criteria (H4DOTC) >> Diagnostic Trouble Code (DTC) Detecting Criteria >> DTC P0442 Evaporative Emission Control System Leak Detected (Small Leak) >> Diagnostic Method

Diagnostic Method

0.04-inch Diagnosis

Mode Z: (Purge Control Solenoid Valve Opening Failure Diagnosis) 

When performing the leakage diagnosis of the EVAP system, the purge control solenoid valve must operate properly. Therefore, mode Z is used to diagnose a stuck open condition of the purge control solenoid valve by monitoring the tank pressure.

Note that if a purge control solenoid valve stuck open fault is detected, the EVAP system leakage diagnosis is cancelled.

DTC 

P0457 Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)

Purge control solenoid valve stuck open diagnosis is performed in mode Z as shown in the figure below.

Fig 1: Purge Control Solenoid Valve Block Diagram
G05018343

DTC 

P0457 Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)

Purge control solenoid valve functional diagnosis is performed by monitoring the tank pressure in mode Z.

Normality Judgment 

Make OK judgment 3 seconds after Mode Z starts, and change to Mode A if OK.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value DTC
(Tank pressure when Mode Z started) - (Tank pressure when Mode Z finished) ≤ 0.4 kPa (3 mmHg, 0.12 inHg) P0457

Judge normal when these calculations are completed.

Abnormality Judgment 

If OK judgment cannot be made, extend Mode Z 16 seconds more, and Judge as NG when all the criteria below are completed in 16 seconds.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value DTC
(Tank pressure when Mode Z started) - (Tank pressure when Mode Z finished) > 0.6 kPa (4.5 mmHg, 0.18 inHg) P0457
Tank pressure when Mode Z started ≤ 1.43 kPa(10.7 mmHg, 0.42 inHg)  
2 or more fuel no sloshing ≥ 40 sec.  

Time Needed for Diagnosis:  16 seconds

Malfunction Indicator Light Illumination:  Illuminates when malfunction occurs in 2 continuous driving cycles.

When judgment for purge control solenoid valve stuck open NG is made, end the evaporative diagnosis. Cancel the evaporative diagnosis when the OK/NG judgment for drain valve stuck closed and purge control solenoid valve stuck open cannot be made in Mode Z.

Fig 3: Identifying Purge Control Solenoid Valve NG Judgment - Mode Z
G05018345

Judge as normal when all are established.

DTC 

P0442 Evaporative Emission Control System Leak Detected (Small Leak)

P0457 Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)

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 atmospheric pressure.

Mode A: (Estimated evaporation gas amount) 

Calculate the tank pressure change amount (P1) when using mode A. After calculating P1, switch to mode B.

Mode B: (Negative pressure sealed) 

Introduce negative pressure in the intake manifold to the tank.

Approx. 0 → -1.4 (0 → -10.5, 0 → -0.41) kPa (mmHg, inHg)

When the pressure above (desired negative pressure) is reached, enters Mode C.

In this case, if the tank pressure does not become the desired negative pressure, judge that there is a large leakage (10 seconds or 25 seconds) in the system.

Abnormality Judgment 

Judge as NG (large leak) when the criteria below are met.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value DTC
Time to reach target negative pressure ≥ 25 sec. P0457
Or mode B time ≥ 10 sec.  
(Min. pressure value in tank when in mode B) - (Tank pressure when mode B started) < -0.3 kPa (-2.5 mmHg, -0.1 inHg)  

Mode C: (Check pressure rise) 

Stop the introduction of negative pressure. (Wait until the tank pressure returns to the start level of P2 calculation.)

Change to Mode D when the tank pressure returns to the start level of P2 calculation.

Judge immediate OK and change to Mode E when it does not return in spite of spending the specified time.

JUDGMENT VALUE

Tank pressure when starting calculation of P2 Time for advanced OK judgment
-1.3 kPa (-9.75 mmHg, -0.38 inHg) 17 seconds

Mode D: (Measure amount of negative pressure change) 

Monitor the tank pressure change amount when using mode D. In this case, the tank pressure increases, (nears atmospheric pressure) because evaporation occurs. However, if any leakage exists, the pressure increases additionally in proportion to this leakage. The pressure variation of this tank is P2.

After calculating P2, perform a small leak diagnosis according to the items below.

When Mode D is ended 

Assign tank variations measured in Mode A and Mode D; P1 and P2, to the formula below, judge small leaks in the system. If the measured judgment value exceeds the threshold value, it is judged to be a malfunction. Judge as NG when the criteria below are completed and Judge as OK when not completed.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value DTC
P2-1.5xP1 P2: Tank pressure that changes every 10 seconds in mode D P1: Tank pressure that changes every 10 seconds in mode A > Value from Map 7 (1) Threshold value: Figure (Remaining Fuel vs Tank temperature) P0442
(1) 1.5: Evaporation amount compensation value when below negative pressure (Amount of evaporation occurrence increases as a vacuum condition increases.)

Map 7 Failure Diagnosis Reference Limit for 0.04 in Leaks for Evaporation Diagnosis 

MAP 7 FAILURE DIAGNOSIS REFERENCE CHART

Fuel temperature & Fuel level 25°C (77°F) 30°C (86°F) 35°C (95°F) 40°C (104°F) 45°C (113°F)
10 L (2.6 US gal, 2.2 Imp gal) 0.28 kPa (2.1 mmHg, 0.083 inHg) 0.29 kPa (2.2 mmHg, 0.087 inHg) 0.31 kPa (2.3 mmHg, 0.090 inHg) 0.31 kPa (2.35 mmHg, 0.092 inHg) 0.32 kPa (2.4 mmHg, 0.094 inHg)
20 L (5.3 US gal, 4.4 Imp gal) 0.31 kPa (2.3 mmHg, 0.090 inHg) 0.32 kPa (2.4 mmHg, 0.094 inHg) 0.33 kPa (2.5 mmHg, 0.098 inHg) 0.35 kPa (2.6 mmHg, 0.102 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg)
30 L (7.9 US gal, 6.6 Imp gal) 0.39 kPa (2.9 mmHg, 0.114 inHg) 0.41 kPa (3.05 mmHg, 0.120 inHg) 0.42 kPa (3.15 mmHg, 0.124 inHg) 0.43 kPa (3.25 mmHg, 0.128 inHg) 0.45 kPa (3.35 mmHg, 0.134 inHg)
40 L (10.6 US gal, 8.8 Imp gal) 0.39 kPa (2.9 mmHg, 0.114 inHg) 0.42 kPa (3.15 mmHg, 0.124 inHg) 0.44 kPa (3.3 mmHg, 0.130 inHg) 0.45 kPa (3.4 mmHg, 0.134 inHg) 0.47 kPa (3.5 mmHg, 0.138 inHg)
50 L (13.2 US gal, 11.0 Imp gal) 0.43 kPa (3.2 mmHg, 0.126 inHg) 0.44 kPa (3.3 mmHg, 0.130 inHg) 0.47 kPa (3.5 mmHg, 0.138 inHg) 0.48 kPa (3.6 mmHg, 0.142 inHg) 0.49 kPa (3.7 mmHg, 0.146 inHg)

Time Needed for Diagnosis:  30 to 100 seconds

0.02-inch 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 atmospheric pressure.

Mode A: (0 point compensation) 

When pressure in tank is high, wait for 0 point 0 kPa (Near 0 mmHg, 0 inHg) to return. Shift to mode B when 0 point returns.

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 → -2.0 kPa (0 mmHg → -15 mmHg, 0 → -0.59 inHg)

When the pressure above (desired negative pressure) is reached, Mode C is entered.

Cancel the diagnosis when the targeted pressure in the tank is not reached.

Mode C: (Negative pressure maintained) 

Stop the introduction of negative pressure and wait until the tank pressure returns to the start level of P2 calculation.

Change to Mode D either when the tank pressure returns to the start level of P2 calculation, or when the predetermined 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. Shift to mode E when pressure returns. Make an advance OK judgment using the value of P2, or cancel, when the pressure in the tank does not return after calculation of P2 is completed even when the predetermined amount of time has passed. When the following conditions are established, judged as OK.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value DTC
Advanced OK judgment 1   P0456
When in Mode D ≥ 30s  
Tank pressure ≤ -1.8 kPa(-13.5 mmHg, -0.53 inHg)  
Advanced OK judgment 2    
When in Mode D ≥ 200 s  
P2 ≥ 0.9 - 1.3 kPa (7 - 9.6 mmHg, 0.28 - 0.38 inHg)  

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 

When the following conditions are established, judged as NG.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value DTC
P1 < Value of Map 7 * Threshold value: Figure (Residual Fuel Amount vs evpdset) P0456

Map 7 Failure diagnosis reference limit for 0.02 in leaks for evaporative emission control system diagnosis 

MAP 7 FAILURE DIAGNOSIS REFERENCE LIMIT CHART

Time evpdset & Fuel level 0 seconds 30 seconds 50 seconds 100 seconds 160 seconds 200 seconds
10 L (2.6 US gal, 2.2 Imp gal) 0 kPa (0 mmHg, 0 inHg) 0.07 kPa (0.5 mmHg, 0.020 inHg) 0.23 kPa (1.7 mmHg, 0.067 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg)
20 L (5.3 US gal, 4.4 Imp gal) 0 kPa (0 mmHg, 0 inHg) 0.07 kPa (0.5 mmHg, 0.020 inHg) 0.23 kPa (1.7 mmHg, 0.067 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg)
30 L (7.9 US gal, 6.6 Imp gal) 0 kPa (0 mmHg, 0 inHg) 0.07 kPa (0.5 mmHg, 0.020 inHg) 0.23 kPa (1.7 mmHg, 0.067 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg) 0.36 kPa (2.7 mmHg, 0.106 inHg)
40 L (10.6 US gal, 8.8 Imp gal) 0 kPa (0 mmHg, 0 inHg) 0.07 kPa (0.5 mmHg, 0.020 inHg) 0.25 kPa (1.85 mmHg, 0.073 inHg) 0.33 kPa (2.5 mmHg, 0.098 inHg) 0.33 kPa (2.5 mmHg, 0.098 inHg) 0.33 kPa (2.5 mmHg, 0.098 inHg)
50 L (13.2 US gal, 11.0 Imp gal) 0 kPa (0 mmHg, 0 inHg) 0.07 kPa (0.5 mmHg, 0.020 inHg) 0.27 kPa (2.0 mmHg, 0.079 inHg) 0.31 kPa (2.3 mmHg, 0.091 inHg) 0.31 kPa (2.3 mmHg, 0.091 inHg) 0 kPa (0 mmHg, 0 inHg)

Normality Judgment 

When the following conditions are established, judged as OK.

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value DTC
P1 > Value of Map 8 * Threshold value: Figure (Residual Fuel Amount vs evpdset) P0456

Map 8 

MAP 8 DIAGNOSIS REFERENCE CHART

Time evpdset & Fuel level 0 seconds 30 seconds 50 seconds 100 seconds 160 seconds 200 seconds
10 L (2.6 US gal, 2.2 Imp gal) 0.13 kPa(1.0 mmHg, 0.039 inHg) 0.47 kPa (3.5 mmHg, 0.138 inHg) 0.56 kPa (4.2 mmHg, 0.165 inHg) 0.56 kPa (4.2 mmHg, 0.165 inHg) 0.56 kPa (4.2 mmHg, 0.165 inHg) 0.56 kPa (4.2 mmHg, 0.165 inHg)
20 L (5.3 US gal, 4.4 Imp gal) 0.13 kPa (1.0 mmHg, 0.039 inHg) 0.43 kPa (3.25 mmHg, 0.128 inHg) 0.55 kPa (4.1 mmHg, 0.161 inHg) 0.55 kPa (4.1 mmHg, 0.161 inHg) 0.55 kPa (4.1 mmHg, 0.161 inHg) 0.55 kPa (4.1 mmHg, 0.161 inHg)
30 L (7.9 US gal, 6.6 Imp gal) 0.13 kPa(1.0 mmHg, 0.039 inHg) 0.4 kPa (3 mmHg, 0.118 inHg) 0.52 kPa (3.9 mmHg, 0.154 inHg) 0.52 kPa (3.9 mmHg, 0.154 inHg) 0.52 kPa (3.9 mmHg, 0.154 inHg) 0.52 kPa (3.9 mmHg, 0.154 inHg)
40 L (10.6 US gal, 8.8 Imp gal) 0.13 kPa(1.0 mmHg, 0.039 inHg) 0.30 kPa (2.25 mmHg, 0.089 inHg) 0.45 kPa (3.4 mmHg, 0.134 inHg) 0.45 kPa (3.4 mmHg, 0.134 inHg) 0.45 kPa (3.4 mmHg, 0.134 inHg) 0.45 kPa (3.4 mmHg, 0.134 inHg)
50 L (13.2 US gal, 11.0 Imp gal) 0.13 kPa(1.0 mmHg, 0.039 inHg) 0.20 kPa (1.5 mmHg, 0.059 inHg) 0.39 kPa (2.9 mmHg, 0.114 inHg) 0.39 kPa (2.9 mmHg, 0.114 inHg) 0.39 kPa (2.9 mmHg, 0.114 inHg) 0.39 kPa (2.9 mmHg, 0.114 inHg)

Time Needed for Diagnosis:  65 to 514 seconds

Malfunction Indicator Light Illumination:  Illuminates when malfunction occurs in 2 continuous driving cycles.