P0442

DTC P0442 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED (SMALL LEAK)




1. OUTLINE OF DIAGNOSIS
Check if there is a leakage in fuel system or not, and perform the function diagnosis of valve.

In this system diagnosis, check for leakage and valve function is conducted by changing the fuel tank pressure and monitoring the pressure change using the fuel tank pressure sensor. When in 0.04 inch diagnosis, perform in the order of mode Z--> mode A--> mode B--> mode C and mode D; When in 0.02 inch diagnosis, perform 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 given, 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 given.




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 856 seconds or more after starting the engine, at a constant speed of 32 km/h (19.9 MPH) or more.
- Pay attention to the fuel temperature and fuel level.

0.02-inch Diagnosis
- Perform the diagnosis after 770 seconds or more after starting the engine, at a constant engine RPM of 68 km/h (42 MPH) or higher, to judge as NG or OK.
- If judgement cannot be made, repeat the diagnosis.
- Be careful of the remaining fuel level.

5. DIAGNOSTIC METHOD

Purge control solenoid valve stuck open fault 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, the purge control solenoid valve must operate normally. Therefore, mode Z is used to diagnose the purge control solenoid valve stuck open condition. Note that if a purge control solenoid valve stuck open fault is detected, the EVAP system leakage diagnosis is cancelled.

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







Normality Judgment
Judge OK and change to Mode A when the criteria below are completed in 3 seconds after Mode Z started.
- evptez ≤ evptezha = 0.4 kPa (3.0 mmHg, 0.12 inHg)
- evptezini ≤ evptezha = 0.4 kPa (3.0 mmHg, 0.12 inHg)

Judge as normal when both calculations are established.




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.
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 purge control solenoid valve stuck open 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.
- The diagnosis is divided into the following five phases.

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.
Approximately 0--> -1.4 kPa (0--> -10.5 mmHg, 0--> -0.41 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 and terminate the evaporative emission control system diagnosis.




Abnormality Judgment
Judge as NG (large leak) when the criteria given are met.




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.

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.







Abnormality Judgment
Judge as NG when the criteria given are met and judge as OK when not met.

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 compensation)
When the pressure in the tank is high, wait for until it returns to 0 point (Near 0 mmHg). 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.
Approximately 0-> -2.0 kPa (0 --> -15 mmHg, 0 --> -0.59 inHg)
When the pressure above (desired negative pressure) is reached, enters Mode C.
When the tank internal pressure does not reach the target vacuum pressure, the diagnosis is cancelled.

Mode C: (Negative pressure maintained)
Stop the introduction of negative pressure. (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 the tank pressure returns to the end level of P2 calculation. If tank internal pressure does not return to level of the P2 calculation end after the predetermined amount of time has passed, make advanced OK judgement or cancel the diagnosis.




Normality Judgment
Judge as OK when the criteria given are met.

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
Judge as NG when the malfunction criteria given are met.







Normality Judgment
Judge as OK when the criteria given are met.

6. DTC CLEAR CONDITION
- When the OK idling cycle is completed 40 times in a row
- When "Clear Memory" is performed

7. MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
- When the OK driving cycle is completed 3 times in a row
- When "Clear Memory" is 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)