Circuit Description
Vapor pressure sensor, VSV for Canister Closed Valve (CCV) and vapor pressure sensor Vacuum Switching Valve (VSV) are used to detect faults in EVAP system. The ECM decides whether there is an abnormality in the evaporative emission control system based on the vapor pressure sensor signal. , DTCs P0441 and P0446 are recorded by the ECM when evaporative emissions leak from the components within dotted line in figure, or when there is a malfunction in either the VSV for EVAP, the VSV for pressure switching valve, or in vapor pressure sensor itself. See Fig 1.
For DTC P0441, ECM closes the CCV and opens the VSV for pressure switching valve, causing vacuum to increase in entire EVAP system. ECM continues to operate VSV for EVAP until vacuum is increased to a specified point at which time the ECM closes the VSV for EVAP. If vacuum did not increase, or if vacuum increased beyond specified limit, ECM judges VSV for EVAP and related components to be faulty. For DTC P0446, when vapor pressure rises to a specified point, the ECM opens the VSV for CCV. Pressure will increase rapidly because of air allowed into the system. No increase or an increase below specified rate of pressure increase indicates a restriction on air inlet side. ECM closes VSV for pressure switching valve. This action blocks air entering 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, ECM will conclude VSV for pressure switching valve did not close. See Fig 2 and Fig 3 . Possible causes are:
- Disconnected, leaking or blocked vacuum hose.
- Vapor pressure sensor circuit is open or shorted.
- Defective vapor pressure sensor.
- EVAP VSV circuit is open or shorted.
- Defective EVAP VSV.
- Vapor pressure sensor VSV circuit is open or shorted.
- Defective vapor pressure sensor VSV.
- Defective charcoal canister.
- Defective ECM.