On the 2003 Lexus SC430, the P0441 and P0446 are set when there is an evaporative emissions leak from the components or when there is a malfunction in either the VSV for the EVAP, the VSV for the pressure switching valve, or in the vapor pressure sensor itself.
P0442 is set when there is an evaporative emissions leak from the components or when the vapor pressure sensor malfunctions.
So- best place to start here is having the EVAP system “smoked”. This is where a machine forces smoke through the system and any leaks can then be more easily found and repaired.
If the smoke test proves no leaks, next test the VSV’s:
VSV for EVAP: 27 – 33 Ohm
VSV for Pressure Switching: 37 – 44 Ohm
If the VSV’s check out ok, replace the Vapor Pressure Sensor. If you are going to skip the smoke test and head straight to the testing, make absolutely certain to carefully inspect the vacuum lines to the VSV’s for any cracks, holes or disconnections. Inspect carefully! A worn or cracked vacuum line is extremely common!
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