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, checking for leakage and valve function is conducted by changing the fuel tank pressure, and monitoring the pressure change using the fuel tank pressure sensor. 0.04 inch diagnosis is performed in the order of mode Z, mode A, mode B, mode C and mode D, and 0.02 inch diagnosis is performed in the order of mode A, mode B, mode C, mode D and mode E.







- 0.04 inch Diagnosis




- Mode Table for Evaporative Emission Control System Diagnosis







- 0.02 inch Diagnosis

2. COMPONENT DESCRIPTION




- 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 valve is forcibly opened by setting the solenoid to ON at the time of diagnosis.







- 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.




When A < B (Solenoid OFF)




When B < C (Solenoid OFF)




When Solenoid is ON




Drain Value
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
- 0.04inch Diagnosis
- 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.
- 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
- Purge control solenoid valve open malfunction diagnosis
DTC
P0457 Evaporative Emission Control System Leak Detected (fuel cap loose/off)

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.

Diagnostic method
CPC 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 Operation
- evptez - evptezha - 0.4 kPa (3.0 mmHg, 0.12 inHg)
- evptezini - evptezha - 0.4 kPa (3.0 mmHg, 0.12 inHg)
Judge normal when both calculations are completed.




Abnormality Judgment
If OK judgment cannot be made, extend Mode Z 16 seconds more, and judge NG when 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

- evptezini, evptez ≤1.43 kPa (10.7 mmHg, 0.42 inHg)
- evptez - evptezha ≤0.87 kPa (6.5 mmHg, 0.26 inHg)
- evptezini - evptezha ≤0.87 kPa (6.5 mmHg, 0.26 inHg)
- No fuel rolling of above 22(0.53 US gal, 0.44 Imp gal) for more than 40 seconds. Judge normal when all the calculations are completed.
- 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.
- The diagnosis is divided into the following five phases.

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, finish the EVAP. diagnosis when judging 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 D, 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. Judge OK when not completed and clear the NG.


- Leak 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.

- The diagnosis is divided into the following five phases.

Mode A: (0 point correction)
Wait until the tank pressure returns to 0 point (near 0 mmHg) when tank pressure is high. Then change to Mode B. If the tank pressure does not return to 0 point in the specified time, cancel the diagnosis.

Mode B: (Negative pressure introduction)
Introduce the negative pressure in the intake manifold to the tank. Approx. 0 -> -2.0 kPa (0 -> -15 mmHg, 0 -> -0.59 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, cancel the diagnosis.

Mode C: (Holding negative 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, or when spending the specified time.

Mode D: (Calculation of negative pressure variation)
By monitoring the tank pressure at Mode D, calculate the pressure variation (P2) and measure the time (evpdset) it takes the tank pressure to return to the detection completing pressure of P2. Then change to Mode E. When the tank pressure does not return to the detection completing pressure of P2 in the specified time, make advanced OK judgment or cancel the diagnosis according to P2 value.




- Normality judgment
Judge OK when the following criteria are satisfied.

Mode E (Calculation of yielded evaporation amount)
Calculate the pressure variation (P1) at the time (evpdset), and make NG/OK judgment according to P1 value (ambiguous determination acceptable).







- Abnormality Judgment
Judge NG when the following criteria are satisfied.







- Normality judgment
Judge OK when the following criteria are satisfied.

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. (For test mode $06)