On the 2003 Toyota Highlander, P0440 is recorded by the ECM when there is an evaporative emissions leak from the components or when the vapor pressure sensor malfunctions.
P0441 and P0446 are recorded by the ECM when there is an evaporative emissions leak from the components. When there is a malfunction in the VSV for EVAP, the VSV for pressure switching valve. Or in the vapor pressure sensor itself.
So best place to start here is to inspect the vacuum lines to the VSVs for any cracks, holes or loose/missing connections. If the visual inspections check ok, test the VSVs:
VSV for pressure switching valve: 30-36 ohms @ 68degrees
VSV for EVAP: 26-30 ohms @ 68degrees
IF the VSV’s ohm out correctly, the fault will lie in the Vapor Pressure Sensor.
Does your vehicle have a similar problem? Get connected to a Live Q&A session with a certified Auto Mechanic and get your answers on this problem now!