How do you fix a P0446 code on a 2001 Toyota 4Runner I replaced the gas cap with a new Factory cap but Check Engine light is still on along with VSC Track and VSC Off lights also on.?

Answer 1

Toyota is having a lot of problems with failures in their EVAP systems. The most common code P0446 pertains to the vent solenoid. This is the solenoid that opens to allow air into the charcoal canister during a purge cycle. The solenoid is normally closed. When it is energized it opens and allows air in. If it sticks open, the pressure sensor on the charcoal canister won't see an increase in vacuum and will set code P0446. However, there are two solenoid valves; 1) the vacuum switching valve VSV closed valve (normally closed) and the 2) canister closed (VSV) valve (normally open). The canister closed valve is located on the air intake.
Test the solenoids by applying vacuum from a hand-held pump. If the valve is normally closed, it should hold vacuum. Apply 12volts and ground to the terminals and see if it opens. Then remove the voltage and apply the vacuum again. Do the same testing procedure for the canister closed valve with opposite results.
If the solenoids don't work properly, replace them with new ones from Toyota.