COMPONENT DESCRIPTION Subaru Impreza WRX GD/GG рестайлинг 2

COMPONENT DESCRIPTION

1. Pressure Control Solenoid Valve

PCV controls the fuel tank pressure to be equal to the atmospheric air pressure.

Normally, the solenoid is set to OFF. And the valve opens and closes mechanically in accordance with the pressure difference between tank and atmospheric air, or tank and canister.

The solenoid which is set to ON forces to open the valve.

Pressure Control Solenoid Valve Operation Diagram. Scheme 274

1. Valve Operation and Air Flow

In the figure below, divided by the diaphragm, the part above X is charged with atmospheric air pressure, and the part below X is charged with tank pressure. Also, the part above Y is charged with tank pressure, and the part below Y is charged with canister pressure.

If the atmospheric air pressure port is A, tank pressure port is B, and canister pressure port is C, the air flows according to pressure difference from each port as shown in the table below.

Pressure Control Solenoid Valve Operation Diagram. Scheme 275

PRESSURE FLOW CHART

Scheme 276

Scheme 277

Scheme 278

Scheme 279

Scheme 280

Scheme 281

1. When A < B (Solenoid OFF) (Scheme 276): Pressure Control Solenoid Valve Operation Diagram
2. When B < C (Solenoid OFF) (Scheme 277): Pressure Control Solenoid Valve Operation Diagram
3. When Solenoid is ON (Scheme 278): Pressure Control Solenoid Valve Operation Diagram
4. CCV (Scheme 279): CCV Operation Diagram
5. Tank Pressure Switching Solenoid One of the atmospheric pressure switching solenoid valves is connected to fuel tank pressure sensor and the other is released to atmosphere. The passage to fuel tank pressure sensor is usually released to atmosphere because the solenoid is set to OFF, but the solenoid which is set to ON closes the passage open to atmosphere. (Scheme 280): Tank Pressure Switching Solenoid Operation Diagram
6. Purpose of this solenoid Fuel tank pressure sensor detects the difference between the atmospheric air pressure and the tank pressure and the ECM monitors the pressure difference. Even if the tank pressure is constant, the atmospheric air pressure varies depending on the driving height, and the pressure signal transmitted to ECM will change. (Scheme 281): Tank Pressure Switching Solenoid Operation Diagram

Especially, in the small leakage [0.5 mm (0.02 in)], minute change in the tank pressure has to be detected. This diagnosis period is long (approx. 29 seconds). And if the driving height changes during the diagnosis, the atmospheric air pressure changes. In this case, it becomes difficult to precisely detect the tank pressure variation, causing erroneous diagnosis. Therefore, using the atmospheric pressure switching solenoid, atmospheric air is sealed between the fuel tank pressure sensor and atmospheric pressure switching solenoid, maintaining the air pressure constant and enabling the detection of minute variation of tank pressure.

Tank Pressure Switching Solenoid Operation Diagram. Scheme 282

Note. ECM also has the atmospheric air pressure sensor, and always monitors atmospheric air. However, as the monitoring range is large, that is, 53 to 107 kPa (400 to 800 mmHg, 16 to 32 inHg) it is not suitable for detection of minute pressure variation. In the case of small leakage diagnosis, the tank pressure variation is very small, that is, 0.13 to 0.27 kPa (1 to 2 mmHg, 0.04 to 0.08 inHg) and the fuel tank pressure sensor is equipped.

0.04-inch Diagnosis

ENABLE CONDITION CHART

0.02-inch Diagnosis

ENABLE CONDITION CHART

1. 0.04-inch Diagnosis

1. Perform the diagnosis only once in more than 856 seconds after the engine start at the constant driving speed of 32 km/h (20 MPH) or more.
2. Pay attention to the fuel temperature and fuel level.

1. 0.02-inch Diagnosis

1. Perform diagnosis in more than 335 seconds after engine start at the constant speed of 68 km/h (42 MPH) or more, and then terminate the diagnosis when judged OK or NG.
2. If not judged OK or NG, repeat the diagnosis until judged OK or NG.
3. Pay attention to the fuel temperature and fuel level.

1. MODE Z (Purge control solenoid valve open malfunction diagnosis)

DTC P0457

1. Purpose of Mode Z

When performing the leakage diagnosis of EVAP system, CPC has to operate normally. Therefore, mode Z is used to diagnose the CPC open fixation.

If the CPC open fixation trouble is detected, the EVAP system leakage diagnosis is cancelled.

EVAP System - System Diagram. Scheme 283

EVAP System Operation Diagram. Scheme 284

1. Diagnostic method

CPC open fixation diagnosis is performed in mode Z as shown in the figure below.

EVAP System - System Diagram. Scheme 285

Scheme 286

1. Normal Operation (Scheme 286): Normal Operation Chart

1. evptez - evptezha < or = 0.4 kPa (3.0 mmHg, 0.12 inHg)
2. evptezini - evptezha < or = 0.71 kPa (5.3 mmHg, 0.21 inHg) Judge normal when both of above calculations are completed.

Scheme 287

1. Purge Control Solenoid Valve Open Fixation (Scheme 287): Purge Control Solenoid Valve Open Fixation Graph
2. evptez - evptezha > 0.6 kPa (4.5 mmHg, 0.18 inHg)
3. evptezini < or = 0.91 kPa (6.8 mmHg, 0.27 inHg)
4. No fuel rolling of above 32(0.79 US gal, 0.67 Imp gal) for more than 35 seconds. Judge normal when both of above calculations are completed.

Normality Judgment

Judge OK and change to Mode A when the criteria below are completed in 3 seconds after Mode Z started.

Judgment Value

JUDGMENT VALUE CHART

1. Diagnosing function of CPC [P0457]

CPC functional diagnosis is performed by monitoring the tank pressure in Mode Z.

Normality Judgment

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

Both diagnostic method and judgment value are the same as PCV normality judgment.

Abnormality Judgment

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

Judgment Value

JUDGMENT VALUE CHART

Time Needed for Diagnosis: 16 seconds

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

Finish the EVAP. diagnosis when making NG judgment for purge control solenoid valve open fixation. Cancel the EVAP. diagnosis when the OK/NG judgment for purge control solenoid valve open fixation cannot be made in Mode Z.

1. Leak Diagnosis DTC P0442 DTC P0456 DTC P0457
2. Diagnostic method
3. 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.
4. The diagnosis is divided into the following five phases.

Mode A; (Estimation of evaporation gas yield)

Calculate the tank pressure variation amount (P1). After calculating P1, change to Mode B.

Mode B; (Seal negative pressure)

Introduce the negative pressure in the intake manifold to the tank.

Approx. 0 --> -1.4 kPa (0 --> -10.5 mmHg, 0 --> -0.41 inHg) (0.04-in diagnosis)

Approx. 0 --> -3.05 kPa (0 --> -22.9 mmHg, 0 --> -0.9 inHg) (0.02-in diagnosis)

When the pressure above (desired negative pressure) is reached, Mode C is entered. In this case, if the tank pressure does not become the desired negative pressure, judge that there is a large leakage in the system.

Judge NG when the malfunction criteria below is completed.

Finish the EVAP. diagnosis when judging large leak (10 seconds or 25 seconds) in 0.04-inch diagnosis. Cancel the diagnosis (10 to 20 seconds) in 0.02-inch diagnosis.

Abnormality Judgment

Judge NG (large leak) when the criteria below are completed in the specified time.

Judgment Value

JUDGMENT VALUE CHART

Mode C; (Check increasing pressure)

Stop the introduction of negative pressure. (Wait until returning target pressure.)

When returning to target pressure, move to Mode D.

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

PRESSURE CHART

Mode D; (Measurement of negative pressure changes)

Monitor the tank pressure variation in Mode D. In this case, the tank pressure increases, that is, the pressure becomes as high as the atmospheric air pressure, because evaporator is generated. 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 small leak diagnosis and change to Mode E if normal. Complete EVAP. diagnosis if abnormal.

1. After Mode D

Assigning P1 and P2, which are tank variations measured in Mode A and Mode B, to the formula below, judge the small leakage of the system. If the measured judgment value exceeds the threshold value, it is judged to be malfunction.

1. 0.04-inch Diagnosis

Abnormality Judgment

Judge NG when the criteria below are completed and judge OK when not completed.

Judgment Value

JUDGMENT VALUE CHART

Map 7 Limit of malfunction criteria for 0.04-inch leak as EVAP. diagnosis.

FUEL TEMPERATURE CHART

1. 0.02-inch Diagnosis

Abnormality Judgment

Judge NG when the criteria below are completed.

Judgment Value

JUDGMENT VALUE CHART

Map 8 Limit of malfunction criteria for 0.02-inch leak as EVAP. diagnosis.

FUEL TEMPERATURE CHART

Normality Judgment

Judge OK when the criteria below are completed.

Judgment Value

JUDGMENT VALUE CHART

Map 9

FUEL TEMPERATURE CHART

If not judged OK or NG, repeat the diagnosis until judged OK or NG.

EVAP System - System Diagram. Scheme 288

Purge Control Solenoid Valve Open/Close Position Graph. Scheme 289

Time Needed for Diagnosis

0.04-inch: 50 - 70 seconds

0.02-inch: 90 - 105 seconds

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

1. When the OK idling cycle was completed 40 times in a row
2. When "Clear Memory" was performed

1. When the OK driving cycle was completed 3 times in a row
2. When "Clear Memory" was performed

Atmospheric purge solenoid function malfunction; Open the pressure control solenoid valve.

1. Memorize the freeze frame data. (For test mode $02)
2. Memorize the diagnostic value and trouble standard value. (For test mode $06)

Detect the open or short circuit of drain valve.

Judge NG when the ECM output level is different from the actual terminal level.

Identifying ECM Components Location. Scheme 290

ENABLE CONDITION CHART

Always perform the diagnosis continuously.

1. Abnormality Judgment

Judge NG when the continuous time of completing the malfunction criteria below becomes more than 2.5 seconds.

Judgment Value

JUDGMENT VALUE CHART

Time Needed for Diagnosis: 2.5 seconds

Malfunction Indicator Light Illumination: Illuminates as soon as the malfunction occurs.

1. Normality Judgment

Judge OK and clear the NG when the malfunction criteria below are completed.

Judgment Value

JUDGMENT VALUE CHART

1. When the OK idling cycle was completed 40 times in a row
2. When "Clear Memory" was performed

1. When the OK driving cycle was completed 3 times in a row
2. When "Clear Memory" was performed

PCV control: Open the PCV solenoid.

Memorize the freeze frame data. (For test mode $02)

Detect the open or short circuit of drain valve.

Judge NG when the ECM output level is different from the actual terminal level.

Identifying ECM Components Location. Scheme 291

ENABLE CONDITION CHART

Always perform the diagnosis continuously.

1. Abnormality Judgment

Judge NG when the continuous time of completing the malfunction criteria below becomes more than 2.5 seconds.

Judgment Value

JUDGMENT VALUE CHART

Time Needed for Diagnosis: 2.5 seconds

Malfunction Indicator Light Illumination: Illuminates as soon as the malfunction occurs.

1. Normality Judgment

Judge OK and clear the NG when the malfunction criteria below are completed.

Judgment Value

JUDGMENT VALUE CHART

1. When the OK idling cycle was completed 40 times in a row
2. When "Clear Memory" was performed

1. When the OK driving cycle was completed 3 times in a row
2. When "Clear Memory" was performed

PCV control: Open the PCV solenoid.

Memorize the freeze frame data. (For test mode $02)

Detect the tank pressure sensor output property abnormality.

Judge NG when there is no pressure variation, which should exist in the tank, considering the engine status.

Tank Pressure Sensor And Tank Pressure Sensor Output Graph. Scheme 292

ENABLE CONDITION CHART

1. Perform the diagnosis continuously in 60 seconds or more after starting the engine.
2. Be sure to check the fuel level and fuel temperature.

1. Abnormality Judgment

Judge NG when the malfunction criteria below is completed.

Judgment Value

JUDGMENT VALUE CHART

If the fuel level (Max. - Min.) in every 60 seconds is less than 2 6, extend 60 seconds more and make judgment with the Max. and Min. fuel level in 120 seconds.

If the difference did not appear though the time extended, extend the time (180,240, 300 seconds) and continue the judgment.

Diagnosis counter will count up when the difference of fuel level (Max. - Min.) is more than 2 G.

Time Needed for Diagnosis: 1 second x 16 times or more

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in two continuous drive cycles.

1. Normality Judgment

Judge OK when the malfunction criteria below is completed.

Judgment Value

JUDGMENT VALUE CHART

1. When the OK idling cycle was completed 40 times in a row
2. When "Clear Memory" was performed

1. When the OK driving cycle was completed 3 times in a row
2. When "Clear Memory" was performed

Purge control solenoid valve control: Purge fixation mode is prohibited.

Memorize the freeze frame data. (For test mode $02)

Detect the open or short circuit of the fuel tank pressure sensor.

Judge NG when out of the standard value.

Tank Pressure Sensor And Tank Pressure Sensor Output Graph. Scheme 293