P0446- Evaporative Emissions Control System Vent Control Circuit Malfunction
- Missing Fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- Incorrect fuel tank vacuum relief valve
Code is detected when VSV for pressure switching valve is ON, ECM judges that there is no
continuity between vapor pressure sensor, fuel tank and charcoal
canister (2 trip detection logic)
The vapor pressure sensor, Voltage Solenoide Valve (VSV) for
Voltage Solenoide Valve (VSV) for canister closed valve (CCV) and Valve
Solenoide Valve (VSV) for pressure switching valve are used to detect
abnormalities in the evaporative emission control system.
The ECM decides whether there is an abnormality in the evaporative emission control system based on the vapor pressure sensor signal.
Diagnostic Trouble Code (DTC) P0446 is recorded by the ECM when there is a malfunction in either the VSV for EVAP,
the VSV for pressure switching valve, or in the vapor pressure sensor
itself, or when evaporative emissions leak from the components within
the dotted line in Fig. 1 below.
The ECM closes the CCV and opens the VSV for pressure switching valve causing vacuum to increase in the entire EVAP system.
The ECM continues to operate the VSV for EVAP until the vacuum is increased to a specified point at which time the ECM closes the VSV for EVAP.
If the vacuum did not increase, or if the vacuum increased beyond the specified limit, the ECM judges the VSV for EVAP and related components to be faulty.