P0456

DTC P0456 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED (VERY 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.






Mode Table for Evaporative Emission Control System 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. 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.















Drain valve
Drain valve controls the ambient air to be introduced to the canister.






3. ENABLE CONDITION












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 (20 MPH) or more.
- Pay attention to the fuel temperature and fuel level.

0.02-inch Diagnosis
- Perform the diagnosis when 125 seconds or more have passed at a constant engine speed of 50 km/h (31 MPH) or higher to judge as NG or OK.
- If judgement cannot be made, repeat the diagnosis.
- Pay attention to the fuel level.

5. DIAGNOSTIC METHOD
Purge control solenoid valve stuck open fault diagnosis