Circuit Description
Vapor pressure sensor, canister closed valve Vacuum Switching Valve (VSV) and pressure switching valve VSV are used to detect faults in EVAP system. ECM determines if a fault is present in EVAP system based on vapor pressure signal circuit. See Fig 1.
DTC P0441 is set when 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 P0446 is set when 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 was no change in pressure, the ECM will conclude the VSV for pressure switching valve did not close. See Fig 2. Possible causes are:
- Disconnected, cracked, damaged or blocked vacuum hose.
- Fuel tank cap installed incorrectly.
- Damaged fuel tank cap.
- Open or short circuit 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.
- Open or short in pressure switching valve VSV circuit.
- Faulty pressure switching valve VSV.
- Damaged fuel tank.
- Faulty charcoal canister.
- Damaged fuel tank overfill check valve.
- Faulty ECM.