Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
The vapor pressure sensor, VSV for canister closed valve (CCV), and 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 pressure sensor signal. DTCs P0441 and P0446 are recorded by the ECM when evaporative emissions leak from the components noted within the dotted line or when there is a malfunction in either the VSV for EVAP, the VSV for pressure switching valve, or in the vapor pressure sensor itself. See Fig 2.
On DTC P0441, 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. DTC is detected when pressure in charcoal canister and fuel tank does not drop during purge control (2 trip detection logic). See Fig 1.
On DTC P0446, when the vapor pressure rises to a specified point, the ECM opens the VSV for CCV. Pressure will increase rapidly because of the air allowed into the system. No increase or an increase below specified rate of pressure increase indicates a restriction on the air inlet side. The ECM closes the VSV for pressure switching valve. This action blocks air entering the fuel tank side of system. The pressure rise on the fuel tank side is no longer as great. If there is no change in pressure, the ECM will conclude the VSV for pressure switching valve did not close. DTC is detected when VSV for pressure switching valve is ON, and ECM judges that there is no continuity between vapor pressure sensor, fuel tank and charcoal canister. Also after VSV for pressure switching valve is turned OFF, pressure in fuel tank is maintained at atmospheric pressure, and when VSV for CCV is ON, pressure in charcoal canister and fuel tank is maintained at atmospheric pressure. See Fig 1 and Fig 3 . Possible causes are:
- Disconnected, damaged or blocked vacuum hoses.
- Fuel tank cap incorrectly installed.
- Fuel tank cap cracked or damaged.
- Open or short in vapor pressure sensor circuit.
- Faulty vapor pressure sensor.
- Open or short in EVAP VSV circuit.
- Faulty EVAP VSV.
- Open or short in canister closed valve VSV circuit.
- Faulty canister closed valve VSV.
- Faulty VSV for vapor pressure sensor.
- Open or short in pressure switching valve VSV circuit.
- Faulty pressure switching valve VSV.
- Cracked or damaged fuel tank.
- Charcoal canister damaged.
- Fuel tank overfill check valve cracked or damaged.
- Faulty ECM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.