P0442
DTC P0442 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED(SMALL LEAK)1. OUTLINE OF DIAGNOSIS
Perform the diagnosis of leakage of fuels system and valve functions.
In this system diagnosis, filter tank pressure is changed. And leakage and normality & abnormality of valve operation are judged by monitoring the pressure change status using the fuel tank pressure sensor. The diagnosis is performed for 0.04-inch diagnosis in the order of Mode A, Mode B, Mode C and Mode D. For 0.02- inch diagnosis, perform in the order of Mode Y, Mode A, Mode B, Mode C and Mode D.
^ 0.04-inch Diagnosis
^ Mode table for Evaporative Emission Control System diagnosis
^ 0.02-inch Diagnosis
2. COMPONENT DESCRIPTION
^ Pressure Control Solenoid Valve
Pressure control solenoid valve maintains the fuel tank pressure equal to the atmospheric air pressure. Normally,the solenoid is set to OFF, and the valve mechanically opens and closes in accordance with the difference between the tank pressure and atmospheric air pressure, and the tank pressure and canister pressure.
The solenoid which is set to ON forces to open the valve.
^ Valve Operation and Air Flow
As in the X parts below, there are the area with atmospheric air pressure above the diaphragm and the area with tank pressure below the diaphragm. Also, as in the Y parts below, there are the area with tank pressure above the diaphragm and the area with canister pressure below the diaphragm. In the table below the air flow from each port in accordance with pressure difference is shown with the atmospheric air pressure port A,tank pressure port B and canister pressure port C.
When A < B (Solenoid OFF)
When B < C (Solenoid OFF)
When solenoid is ON
^ Drain valve
Drain valve controls the ambient air to be introduced to the canister.
3. ENABLE CONDITION
^ 0.04-inch Diagnosis
^ 0.02-inch Diagnosis
4. GENERAL DRIVING CYCLE
^ 0.04-inch Diagnosis
- Perform the diagnosis only once in more than 856 seconds after the engine start at the constant driving speed of 32 km/h (19.9 MPH) or more.
- Pay attention to the fuel temperature and fuel level.
^ 0.02-inch Diagnosis
- Perform diagnosis in more than 770 seconds after engine start at the constant speed of 68 km/h (42 MPH)or more, and judged OK or NG.
- If not judged OK or NG, repeat the diagnosis.
- Pay attention to the fuel level.
5. DIAGNOSTIC METHOD
^ Diagnosing Function of Purge Control Solenoid Valve
DTC
P0457 Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)
Purpose of Mode Z
When performing the leakage diagnosis of EVAP system, purge control solenoid valve have to operate normally. Therefore, mode Z is used to diagnose the purge control solenoid valve open fixation. If purge control solenoid valve open fixation trouble is detected, the evaporation system leakage diagnosis is cancelled.
^ Diagnosing function of purge control solenoid valve [P0457]
Purge control solenoid valve functional diagnosis is performed by monitoring the tank pressure in Mode Z.
^ Normality Judgment
Judge OK when the following criteria are satisfied in 3 seconds after Mode Z started, and change to Mode A.
^ Normal
Judge normal when the following conditions are completed at once.
^ evptez. evptezha. 0.4 kPa (3.0 mmHg, 0.12 inHg)
^ evptezini. evptezha. 0.71 kPa (5.3 mmHg, 0.21 inHg)
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.
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.
^ Purge control solenoid valve open fixation
^ Leak Diagnosis
DTC
P0442 Evaporative Emission Control System Leak Detected (small leak)
P0457 Evaporative Emission Control System Leak Detected (fuel cap loose/off)
^ 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.
^ This diagnostic method consists of 5 steps.
Mode A: (Estimation of evaporation gas yield)
The amount of change of tank pressure (P1) in Mode A is calculated. 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)
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 and judge as large leak (10 or 25 seconds).
Abnormality Judgment
Judge NG (large leak) when the criteria below are completed in the specified time.
Mode C: (Check increasing pressure)
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.
Mode D: (Measurement of negative pressure changes)
Monitor the pressure variation in the tank in Mode Z. 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.
- 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.
Abnormality Judgment
Judge NG when the criteria below are completed and judge OK and clear the NG when not completed.
Leak diagnosis
DTC P0456 Evaporative Emission Control System (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.
^ This diagnostic method cosists of 5 steps.
Mode A: (0 point correction)
Wait until the tank pressure returns to 0 point (around 0 mmHg) when the tank pressure is high. Change to Mode B when the tank pressure becomes 0. Cancel the diagnosis when the tank pressure does not return to 0 point in spite of spending the specified time.
Mode B: (Introduce negative pressure)
Introduce the intake manifold negative pressure to fuel tank.
About 0 -> .2.0 kPa (0 mmHg ->.15 mmHg, 0 ->.0.59 inHg)
Change to Mode C when the tank pressure becomes the pressure (desired negative pressure) above. Cancel the diagnosis when the tank pressure does not become the value above.
Mode C: (Hold negative pressure)
Stop introducing the negative pressure and wait 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 or when spending the specified time.
Mode D: (Calculation of negative pressure variation)
Monitor the tank pressure on Mode D, and calculate the tank pressure variation (P2) and time until it returns to the end level of P2 (evpdset). When it returns, change to Mode E. Make advanced OK judgment or cancel depending on the P2 level, when it doesn't return in spite of spending the specified time.
Normality Judgment
Judge OK when the criteria below are completed.
Mode E: (Calculation of evaporation gas yield)
Calculate the tank pressure variation P1 in time evpdset, judge NG/OK from P1 value. (Gray judgment possible)
Abnormal judgment
Judge NG when the criteria below are completed.
Normality Judgment
Judge OK when all the malfunction criteria below are completed.
6. DTC CLEAR CONDITION
^ When the OK idling cycle was completed 40 times in a row
^ When "Clear Memory" was performed
7. MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
^ When the OK driving cycle was completed 3 times in a row
^ When "Clear Memory" was performed
8. FAIL SAFE
None
9. ECM OPERATION AT DTC SETTING
^ Memorize the freeze frame data. (For test mode $02)
^ Memorize the diagnostic value and trouble standard value.